[SQUASHED] Custom init script support with Omni extras

Based on a stripped-down version of Cyanogenmod's initscript extras

Change-Id: I5d4dc3da437f6fe3a86d5dada563c1df8d20c902

Clean up cruft in custom initscript extras

ANDROID_CACHE is only in CM's dalvik and we have yet to determine if
we want that feature

Also remove Omni branding

Change-Id: I9c02ed2a2376a1f0500d8f156929a8e511aa6db5
common: Add our overlays