Re-work the way we distribute the header and firmware files. The header
files may be accessed by everyone but the firmware may only be used by
owners of our device. Create a header only repository with all the header
versions of the firmware and create tarballs for specific releases that
will be provided to our customers. Use COMPATIBLE_MACHINE to pick the right
firmware and API version depending on sysmoBTSv1 and sysmoBTSv2.
