CommitResource: Delegate to ProjectResource

Other child resources, such as RevisionResource, use delegation rather
than inheritance to refer to their parent collections. This allows us
to use more sensibly named methods; for example, it is not obvious
that what myCommitResource.getNameKey() is referring to is actually
the project name key.

Change-Id: I2aa58246afd22ef7bd0f437c6cfe7233b825f976
3 files changed