Search Project by Project Group

This patch allows us to search projects by project group, as well a
few unit tests to make sure the results are sane.

I'm not a huge fan of copying most of the boilerplate code from the
base db api into the project groups api. Suggestions are welcome.

Change-Id: If10cf46fcfc5c47e8de8fa85f8dd9b11869d5ce0
Merge "Search Project by Project Group"