Updated to defines to align with FrSkySPort.h

Reordered defines.  Add a few missing defines that might be useful.
Changed SENSOR_ID_FLVSS to A1.
Added DEBUG_AVERAGE_VOLTAGE

Added DEBUG_AVERAGE_VOLTAGE to enable/disable "Number of samples for
voltage average" message in release build.
Added support to debug base and custom mode

Added support to debug base and custom mode
Merge pull request #1 from ddyeakley/master

Updated to defines to align with FrSkySPort.h plus a few other misc changes