Try out sphinx-based documentation.
Add pip requirements file.
Move doc/requirements.txt to root folder.
Unversion extraneous xml.
Use `autodoxygenfile` and `autodoxygenindex` command.
Add script to autogenerate reference documentation.
Add missing Python module.
Remove file (name is wrong.)
Fix table of contents.
Add missing reference doc.
Autogenerate reference documentation pages.
Update templates for the reference documentation.
Fix python path.
Update autogenerated reference documentation pages.
The index page is not generated automatically.

Instead we hook up the autogenerated reference documentation in the index page.
Unversion old `ref_doc_generation.py` (moved to another location).
Update the `index` page of the documentation.
Merge pull request #68 from DO-CV/maint-update-documentation

[DOC] Add Sphinx-based documentation (experimental).