Include mGerrit as prebuilt apk

Patch Set 2: update mGerrit version

Breaks mGerrit's dependancy on AOKP updates for it own updates. Because
the apk is signed with the market key then the PlayStore will handle
the updates.

Change-Id: I6c86991062e0c95a9a783320e89a2cf6d0169047
Merge "Include mGerrit as prebuilt apk" into jb-mr2
Merge remote-tracking branch 'upstream/jb-mr2' into jb-mr2