add superadmin apis for managing tenants.  Added a db table for
tenants and did some refactoring so common db operations and
generation of ids can be re-used.
fix incomplete refactoring, cleaning up tenant APIs and
make sure everything that needs to be started is started.
edge case around missing tenant ids.
correcting doc inaccuracies and ambiguities.
Merge pull request #239 from continuuity/feature/superadmin-apis

Feature/superadmin apis