Cleanup imports in "traitsui.editors.*"

[rahulporuri]

There were a number of FIXMEs in the imports in traitsui.editors.* which this PR addresses and cleans up - converting them into explicit imports instead of implicit imports.

[rahulporuri]

The following seg fault is observed on travis - and this looks intermittent so im restarting the job for now

test_livemodal_view_application_ok (traitsui.tests.test_view_application.TestViewApplication) ... Fatal Python error: Segmentation fault
Current thread 0x00007fec931a4700 (most recent call first):

  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/ui_base.py", line 86 in add_button
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/ui_live.py", line 202 in init
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/ui_base.py", line 298 in display_ui
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/ui_live.py", line 75 in _ui_dialog
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/ui_live.py", line 59 in ui_livemodal
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/toolkit.py", line 165 in ui_livemodal
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/ui.py", line 238 in ui
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/view.py", line 454 in ui
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/view_application.py", line 136 in __init__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/view_application.py", line 94 in view_application
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/qt4/toolkit.py", line 243 in view_application
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/tests/test_view_application.py", line 76 in view_application
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/traitsui/tests/test_view_application.py", line 163 in test_livemodal_view_application_ok
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/case.py", line 605 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/case.py", line 653 in __call__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 122 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 84 in __call__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 122 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 84 in __call__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 122 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 84 in __call__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 122 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/suite.py", line 84 in __call__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/runner.py", line 176 in run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/main.py", line 256 in runTests
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/main.py", line 95 in __init__
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/unittest/__main__.py", line 18 in <module>
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/execfile.py", line 183 in run_python_file
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/execfile.py", line 113 in run_python_module
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/cmdline.py", line 627 in do_run
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/cmdline.py", line 483 in command_line
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/cmdline.py", line 756 in main
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/site-packages/coverage/__main__.py", line 8 in <module>
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/runpy.py", line 85 in _run_code
  File "/home/travis/.edm/envs/traitsui-test-3.6-pyqt/lib/python3.6/runpy.py", line 193 in _run_module_as_main
Command "python -X faulthandler -W default -m coverage run -p -m unittest discover -v traitsui" exited with segmentation fault (-11)

[aaronayres35]

LGTM