Manta: Toggles overlay

add common tab stuff to overlay and switch to just common.mk,
because the common_tablet was still the one I was getting.
common_tablet.mk only inherits the common_tablet overlay and
common.mk.

Change-Id: Iaeb65544b462c807bf857dad749b1acb5e09cf64
Merge "Manta: Toggles overlay" into jb-mr1
Merge remote-tracking branch 'upstream/jb-mr1' into jb-mr1