v2.2.0

SAGE-1514: split the output deb

When installing the (previous) RPi deb into a Docker environment the build
would often fail.  This is presumed because the original Debian package
is very large and has lots of files.

Therefore we are splitting into 4 debs:
- boot (supporting PxE booting)
- OS - /usr/lib/firmware directory
- OS - /usr/lib (other - excluding firmware)
- OS - all other files
- Meta package (that depends on the above 4)