Adding support for the more generic PreciseRevision

Right now a package can have a MajorRevision or a FullRevision.
A MajorRevision is just a special case of FullRevision, but they're
stored and accessed differently, for no benefit.
Adding support for a derived PreciseRevision, which (hopefully) will
eventually be the only true way to do revisions in studio.

Change-Id: I48c8d7857a190c4cbf52e67779a6a2c2cf3aad37
3 files changed