Move to omni-armv6

Change-Id: Ia480af56cf036e568bc69ce3a6a07c70e33d5a7c
manifest: add a general github remote

Just makes it a bit easier to track personal repos and those from themuppets, etc
in local_manifests.

Change-Id: I05105b94288e922470c3c57d442867600ba10fe3
default: Fork android_system_extras

Change-Id: I532c0adca3e35a37b8e6cfc2fe9c4d2701b37962
Shift to omni-armv6 system/core

Change-Id: Iee13b83fbf38055544471b5fd28305097e906beb