optional encryption password sync (1/2)

Option to use 2 different tokens for encryption and locking.
Allows convenient usage and strong encryption at the same time.

Inspired by reading next:
https://santoku-linux.com/howto/mobile-forensics/how-to-brute-force-android-encryption

Related discussion:
http://code.google.com/p/android/issues/detail?id=29468

Change-Id: I87f12bb1644f3abcbbd6b23813bbbf2cd58855df
Signed-off-by: Dan Trifan <jimsth@gmail.com>