Include LMS and CMS SDKs in the developer documentation

The T&L team have expressed that our productivity is impacted by not having good access to technical documentation. The Open edX code base has a lot of useful documentation strings that would be incredibly valuable to have as a browsable documentation set. This would also be equally beneficial to the whole Open edX community.

Currently the bulk of the code-generated developer documentation is for lib/common which is only a small part of the code:

http://edx.readthedocs.org/projects/edx-developer-guide/en/latest/common-lib.html

My understanding is that the documentation doesn't build currently so clearly fixing that is a prerequisite. There is a sense that developers would prioritize this now if there was a belief that it would become a valuable resource for everyone.