Copy generic SMA data protocol classes from .sunnynet package into new
.protocol package, in preparation of shaing with SMANet frame
implementation.
Add empty byte array to SmaUtils so it can be shared between SunnyNet
and SMANet.
Turn SmaPacket into just a SMA packet, rather than the entire SunnyNet
frame that it was before. This class can then be used for SMANet frame
encoding.
Create SmaDataFrame interface and SmaSunnyNetFrame implementation, based
on code in the old .sunnynet.SmaPacket class. A new SmaNetFrame
implementation can then share a common API with SmaSunnyNetFrame.