added initial work on network coding.

Refactor network coding
Simplify test result handling
Add window size to ACK, ensure only one new degree of freedom per packet
Reduce seq to a rotating uint8
Add network coding test app to the build
Start using network coding over the radio link
Dont resend packets over a 'reliable' link
Add network coding stats to html output
Reject packets with a jump in sequence numbers
Remember the time that each packet was added
Tweak radio link to reduce peak latency
Allow receiver to hold 64 packets