Refactored AverageWindDecoder - it now implements MessageDecoder. Refactored AverageWind - it now uses milliseconds and knots, instead of packed MMperSec and tenths of a second. It also exposes its attributes now. Added (un)packAverageWindPeriod to AC35UnitConverter. Added AverageWindDecoderTest. issue #35 #36 #story[1095]