Allow sphinx to be run without MantidPlot.

The documentation for the mantidplot & the screenshots will be missing
but it can be useful to be able to do this to aid debugging.
Refs #9624
Snapshot what is generated by the old sphinx autogen_api mechanism.

The files will now live as first-class citizens allowing more controlled
customization of some files.
Refs #9624
Minor alteration to main index file

Use the standard for H1 titles.
Refs #9624
Add in the old attempts to for hooking up breath & doxygen...

to Sphinx. We don't want to lose the information.
Refs #9624
Add skipping mechanism autodoc

It currently just skips __init__ like the old one did
Refs #9624
Fill in the version string in the Sphinx config

Refs #9624
Fix warning about missing blank line.

Refs #9624
Clear warning about error in toctree directive.

Refs #9624
Add calibration pages from the old sphinx docs.

Refs #9624
Include api/python in the main toctree

Refs #9624
Add the changes.rst document from the old sphinx docs.

Refs #9624
Remove the old sphinx targets.

Refs #9624
Rename a file to avoid a name clash on case-insensitive filesystems.

Refs #9624
Swap doctest blocks for standard code blocks in calibration

Refs #9624
Merge remote-tracking branch 'origin/feature/9624_python_docs_to_static_rst'