Add manta to menu, update overlay, update fingerprint to 4.2.1

Change-Id: Ieacf2d2b94815fa5edeccd0fd802654158d09e6a
README: Update branch to reflect mr1

Change-Id: I917d3fa33cf65355a9c8afca74d4b98bbe97ab18
Merge remote-tracking branch 'upstream/jb-mr1' into jb-mr1