Add ifdtool, utility to read / modify Intel Firmware Descriptor images

Change-Id: Ie78b97bf573d238d0dff9a663e774deb1b7dea44
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/272
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>