Josh/2 one way transmission

See merge request !2

The main communications issues were that my signal timings were self-contradicting.
I can now send *some* communications across the line, however bit slip is still causing some issues

In order to hopefully identify the source of the ticking...

It looks like I can reasonably reliably detect pulses of 200μs, but I should detect these with a +-25% range for reliable detection I reckon

This was done with two micro:bits connected with one wire on PIN 1

Wrote very small amount of demo code in main() to test pairing

This completes the pairing functionality

I had some uninitialised member bugs in my buffer implementation...

I seem to have a bug in my ManchesterEncoder, that or I've introduced one