Boot: Use the MCUBoot version of the imgtool.

Uses the MCUBoot version of the imgtool. Adds a Python wrapper script
to work around its altered interface.

Change-Id: I9dc98f254f26de8d379e544a2c59fa6f08d42341
Signed-off-by: Balint Matyi <Balint.Matyi@arm.com>
4 files changed