Clean up documentation

Switch to manually generated rst files for the API documentation so we
do not expose private parts of the library.

Fix formatting of usage.rst

Convert bullet list to section headers to fix rendering issues and make
the docs more readable.

Fix formatting of docstrings in classes exposed in the docs to eliminate
warnings/errors from Sphinx.

Add history.rst

Change-Id: I6f500775f801558f7c0c29f180b60f83a7150e02
Merge "Clean up documentation"