compilation fixes & removal of RFM96 library

These are 2 commits so you can decide not to integrate both.
One is compilation fixes: it now compiles and I can see a LED flashing on the Arduino. I can't verify yet(!) if it indeed is operating correctly as I have it all not setup correctly here.
The other commit is the removal of the RFM69 files from the repeater project: here at my local arduino sketchbook i've got https://github.com/philcrump/UKHASnet_RFM69_Synchronous checked-out into libraries/  This way I hopefully always have the latest version of it for all my projects.