jf: Improvements to Loki support

Add loki_flash targets for installing patched boot images instead of dd.
loki_flash verifies the image has been properly patched as one extra safeguard.
Update releasetools.py to add updater-script commands that mimic backuptool.sh.
Move most of the black magic out of loki.sh and into the updater-script.
loki.sh is only used to patch, if necessary, and flash a boot.img.
Update loki.sh to report when it has an error.  Use an assert to check for this.
Update nfcee_access.xml to include Google Wallet.
Update Loki LICENSE to plain text instead of HTML.

Patch Set 2: Make loki.sh exit 1 in case of an invalid bootloader.
Patch Set 3: Remove /system/etc/valid_bootloaders after install.  It serves
no purpose outside of installation.
Patch Set 4: Redo patch set 2.  Update loki.sh to support developer models by
flashing an unpatched boot.img when a non-Loki bootloader is detected.
Patch Set 5: Minor style cleanup.
Patch Set 6: White space cleanup in loki_flash.c.  Revert Google Wallet change.

Change-Id: I18e7717c6f459af20e629d4b806599e9a8dca356