jewel: support building recovery

To be used in conjunction with recovery files provided by s4-common

CWM and TWRP: leaves 16kb footer at the end of /data to store
encryption information (if needed).

TWRP: supports backup and restore of encrypted /data partition
and includes USB OTG as a storage option.

Change-Id: I112e9412cb3df67a435c833efc05704132444d8a