Separate Android Encryption Password from Lockscreen Password

This permits the use of a different (hopefully longer and more complex!) encryption
password, while using a simpler (and easier to type) lockscreen password.

Change-Id: Ib8c62c8eb4c86cd9e0117444231e8139c08ad1b6
Merge remote-tracking branch 'omni/android-4.4' into android-4.4