Brought back old test code that was working

Corrected sync preamble. ...

Brought in original legacy C code for reference

Tweaks to legacy learn feature

Rewrote legacy.py to use new modulation code. ...

Not yet tested on a real Raspberry Pi

Started work on OOK support. ...

Ported C code into radio.py
Split out monitor and switch. Monitor.py is now just a monitor.
Switch.py needs more work to make it just a switch.
legacy.py will be a demo app for legacy (green button) devices.

Removed and tweaked a lot of trace messages to make it less noisy

Added RESET at start to reset the radio to a known clean state. ...

Added a SWITCH ON/OFF message every 5 seconds.
Re-tested and reports now seem to be a reliable 10 seconds.

Improved message decoding. ...

Now builds a dictionary of seen devices.
Monitor FFFFFF messages removed, not needed.
Catches bad payloads and prints a warning rather than crashing.
Accepts and responds to a JOIN command.
Message and value encoders written and working.
Message and value decoders written and working.

Message decoder added. ...

Messages polled at a faster rate.
Now see unsolicited switch change messages from MiHome AdapterPlus.
Removed a lot of debug messages.
Real value decoding now working.

Added source files from first working tests