The SB API documentation migrated to sphinx

Hi all,

some of you might have noticed that over the weekend we migrated the SB API documentation over to sphinx: LLDB Python API — The LLDB Debugger

This change will require some (minor) changes to the current workflow:
1. docstrings in the SWIG (*.i) files should be written in reStructuredText. [1] has an overview of the reStructuredText syntax.
2. Documenting functions should be done using the sphinx approach [2].
3. You need the sphinx-automodapi plugin to build the API docs. The docs are now also built as part of the normal LLDB website (the target name is `docs-lldb-html`).

There are still a few things I need to figure out (mostly how to properly document the special `__XZY__` functions and our global enum variables), but otherwise this website is mostly ready. Let me know if you run into any issues.

The old API documentation is still online but will redirect soon to the new API documentation.

A very big thanks to Andrei Lebedev for taking care of doing all the server maintenance on the build server!

- Raphael

[1] reStructuredText Primer — Sphinx documentation
[2] Writing docstrings — Sphinx-RTD-Tutorial documentation