update to 4.4.3

Change-Id: Ie1698fba64e7b03026c8c3ad3d7a065134c954bf
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>
Track CMs external_chromium_org
Update remotes for 4.4.3
Update readme
Track CMs hammerhead kernel for now.
Update for 4.4.3