analyzer: add initial Sphinx configuration

This is just the output of sphinx-quickstart. Now all that is needed
to begin converting the analyzer docs to reST is the server-side setup.

The analyzer folks have asked me to keep this segregated from the other
clang docs since the analyzer is a logically separate project (and has
its own separate web page) even though it resides in the clang tree.

llvm-svn: 171425