Update software serial to support RX, TX or RX&TX modes. Update serial
API to allow on-the-fly changing of serial port mode. Update HoTT to
change serial port mode when transmitting.
HoTT packet structures, checksum is always sent by the response sending
code. Reduce ram usage by 173+ bytes. Corrected accreditations.
Updating documentation to match code. Replaced comments that commented
out code with #ifdef blocks because commented out code is not found by
refactoring tools.