optional cross-check between OTA radio images and board-info.txt

Adds a python script which checks the version of each radio image
added with the new add-radio-file-checked macro against a file
containing sha-1 -> version string mappings and the contents of
board-info.txt, so that the build can fail if board-info.txt and the
OTA images are out of sync.

Change-Id: Icb61dc2adefc240ced9059941582c23b629089c0