Config system improvements: compositional config, added scenes_dir, removed config_dir, fixed eqa test

[mathfac]

• How to initialize environment outside of main repo? #63, Have a prefix for loading up configs to streamline the process #25: Added scenes_dir parameter to Config to have no requirement of data symlink or data directory in working directory. scenes_dir will be used as prefix for scene_id during episodes dataset loading.
• Added overwriting options argument to get_config that unblocks parameter sweeping and experimentation capabilities from command line
• [Feature Request] Compositional configuration #29: config_file path can be comma separated list of configs that will be merged in exact order. That will help to use separate configs for dataset specification and sensors setups. String with commas was chosen because that make it easy to pass list of configs as script argument.
• To make habitat-api easier to as package we decided to get rid of forcing loading of configs from config_dir param
• Habitat-Sim change causes failing test #75: fixed unit test caused by latest habitat-sim update

Caution: with this change all config paths will be specified in new way: tasks/poingoal.yaml => configs/tasks/pointgoal.yaml

How Has This Been Tested

pytest
black . --line-length 79;mypy . --ignore-missing-imports;pycodestyle;flake8

============================================================================================================ test session starts =============================================================================================================
platform linux -- Python 3.6.4, pytest-4.4.1, py-1.5.2, pluggy-0.9.0
rootdir: /private/home/maksymets/habitat-api, inifile: setup.cfg, testpaths: test
plugins: xdist-1.25.0, forked-0.2
collected 37 items

test/test_baseline_agents.py ..                                                                                                                                                                                                        [  5%]
test/test_config.py .                                                                                                                                                                                                                  [  8%]
test/test_dataset.py .........                                                                                                                                                                                                         [ 32%]
test/test_habitat_env.py .........s                                                                                                                                                                                                    [ 59%]
test/test_habitat_example.py ...                                                                                                                                                                                                       [ 67%]
test/test_install.py .                                                                                                                                                                                                                 [ 70%]
test/test_mp3d_eqa.py ...                                                                                                                                                                                                              [ 78%]
test/test_pointnav_dataset.py ...                                                                                                                                                                                                      [ 86%]
test/test_sensors.py ...                                                                                                                                                                                                               [ 94%]
test/test_trajectory_sim.py ..                                                                                                                                                                                                         [100%]
========================================================================================================== short test summary info ===========================================================================================================
SKIPPED [1] test/test_habitat_env.py:318: unconditional skip

=================================================================================================== 36 passed, 1 skipped in 210.82 seconds ===================================================================================================

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[erikwijmans]

Same comment/feelings about this function as above.

[mathfac]

Addressed the comments. Added support of config list, corrected scene_path, added overwriting options, added EQA dataset changes, adopted quaternion suggestion. Retested:

======================================================================================================================================================= test session starts =======================================================================================================================================================
platform linux -- Python 3.6.4, pytest-4.4.1, py-1.5.2, pluggy-0.9.0
rootdir: /private/home/maksymets/habitat-api, inifile: setup.cfg, testpaths: test
plugins: xdist-1.25.0, forked-0.2
collected 38 items

test/test_baseline_agents.py ..                                                                                                                                                                                                                                                                                             [  5%]
test/test_config.py ..                                                                                                                                                                                                                                                                                                      [ 10%]
test/test_dataset.py .........                                                                                                                                                                                                                                                                                              [ 34%]
test/test_habitat_env.py .........s                                                                                                                                                                                                                                                                                         [ 60%]
test/test_habitat_example.py ...                                                                                                                                                                                                                                                                                            [ 68%]
test/test_install.py .                                                                                                                                                                                                                                                                                                      [ 71%]
test/test_mp3d_eqa.py ...                                                                                                                                                                                                                                                                                                   [ 78%]
test/test_pointnav_dataset.py ...                                                                                                                                                                                                                                                                                           [ 86%]
test/test_sensors.py ...                                                                                                                                                                                                                                                                                                    [ 94%]
test/test_trajectory_sim.py ..                                                                                                                                                                                                                                                                                              [100%]
===================================================================================================================================================== short test summary info =====================================================================================================================================================
SKIPPED [1] test/test_habitat_env.py:318: unconditional skip

============================================================================================================================================= 37 passed, 1 skipped in 176.51 seconds ==============================================================================================================================================