Moved function PrefixFree#asInt:(Bit):Int to method Bit#asInt:Int.
Renamed object PrefixFree to PrefixFreeBigInt.
Simplified type of PrefixEncoder#append(Enum<?> e).
Refactored logic.common.PrefixEncoderImpl to extend Scala class PrefixEncoderWrapper that wraps PrefixEncoderTrait.