g3: add bump script

* auto bumps boot and recovery images
* to enable for your variant, set TARGET_REQUIRES_BUMP in BoardConfig

Change-Id: Ib04dda56564c8b89f9c24a75ef5dffc43073b063
[TEMP] g3: disable overlay settings that don't exist

Change-Id: I781a6c39286424f4e5312aa73395142312a6546d
Merge branch 'cm' into HEAD

Conflicts:
	overlay/frameworks/base/core/res/res/values/config.xml

Change-Id: If37c09180c0103a24d3c937d3dfc5a2fe5d54a91