Recovery: Loki patching support

Add support for automatically checking and making loki images
for locked bootloader bypass on loki supported devices. Loki
support is enabled with ENABLE_LOKI_RECOVERY.

Change-Id: I81fe267d58f0dda18a790e25df223f011dca3e37
Merge "Recovery: Loki patching support" into cm-10.2
recovery: nandroid: implement preference for backup_format

ro.cwm.prefer.backup_format takes:
dup (dedupe)
tgz (tar + gzip)
(i.e. setprop ro.cwm.prefer.backup_format tgz)

-If nothing is specified or the above is not matched then tar is used.
-If the user specifies a default_backup_format then that is used.

Change-Id: I935d6cc732c5ef2b1d0d44f5459425e85702e710