This PR initializes sphinx autodocs for each of the scripts/*.py files. This PR also adds instructions on how to build the docs, and standardizes the docstrings. It also moves the gaps directory up to the top level out of the old docs folder. Closes #151, and would be good to have as part of #154.

Most of the changes are creating the files below, and removing colons from docstrings. A good check would be if you can build the docs themselves, they should still be pretty rough around the edges (we'll build on it in future PRs).

Autodoc files that correspond to a script.

• docs/analysis_doc.rst
• docs/create_ar_deployinst_doc.rst
• docs/create_cyclus_input_doc.rst
• docs/dakota_input_doc.rst
• docs/dataframe_analysis_doc.rst
• docs/index.rst
• docs/merge_coordinates_doc.rst
• docs/output_metrics_doc.rst
• docs/predicting_the_past_import_doc.rst
• docs/random_lifetime_extension_doc.rst
• docs/scripts_outline.rst
• docs/transition_metrics_doc.rst
• docs/transition_plots_doc.rst

This PR does not:

1. Add docs for the tests. Add Test Docs #161
2. Document the other projects in the repository. Add narrative to the docs #159
3. Include examples. Add docs examples #160
4. Establish narrative on the existing docs. Add narrative to the docs #159
5. Functionalize and document the create_cyclus_input.py script. Functionalize and document create_cyclus_input.py #162