ota: Validate any installed data's signature against our own

Try to prevent incompatible-signature system quirkiness

Change-Id: I73402d963a1b57ad0ee3c68ced4f2d7f074f927f
common: Set property for the CM releasetype

Set ro.cm.releasetype based on the deteremined releasetype of the
build.

Change-Id: I2c1aa7181f42342594bd6d5dc5f5252220ed3497

Conflicts:
	config/common.mk