[airborne] add pprz_version and send it with BOOT

At build time define the Paparazzi version and git sha1 and make that usable in airborne code.
The BOOT message now contains the version encoded in uint16_t as `(PPRZ_VER_MAJOR * 100 + PPRZ_VER_MINOR * 10 + PPRZ_VER_PATCH)` which is fine as long as we don't have one of these fields with a value higher than 10.