Combine RFM69/RFM9X libraries

[jerryneedell]

Please take a look at the issue in the RFM9X library adafruit/Adafruit_CircuitPython_RFM9x#92 and comment there.

[jerryneedell]

new library https://github.com/adafruit/Adafruit_CircuitPython_RFM.git has been created.
The initial code has been submitted as a PR adafruit/Adafruit_CircuitPython_RFM#1