Add workspace lock from upstream

Change-Id: Iff93293db8a112b5224dd91db5164f5348576266
Revert "Trebuchet: Lock homescreen"

This reverts commit 748d20203ac16d2d5080ef0bd93dea9a767948da.
Merge remote-tracking branch 'sgt7/cm-10.1' into cm-10.1-dev