Added doctree for Sphinx documentation

refs #16557

Started the sphinx documentation. Created docs folder and added sphinx to
requirements.txt
Added draft files for the api and model documentation

refs #16557
Removed extra source folder

refs #16557
Fixed a typo in requirements.txt

refs #16557
Updated documentation structure

refs #16557

Added several directories, moved the draft docs, and updated the index file.
Also deleted the extra makefile
Fixed sphinx documentation

refs #16557

Moved directories to the proper places, edited the index so that it knows where
to find files, added titles to the files so that it would document them
correctly
Added the planning directory to the toc tree, removed dirs from it

refs #16557
Copyright should be OSU OSL, not individual devs

refs #16557
Sub-toctree gives better structure to main TOC

The toctree in the included planning.rts allows nesting the planning
docs under a 'planning' category on the index.

refs #16557
Doc titles should indiecate draft status

refs #16557