IForwardErrorCorrectionInfo: added interface and ConvolutionalCoder implements it.
XIModulation replaced with IModulationScheme.
XModulation: followed recent changes.
ISignalBitModel (merge later): added getForwardErrorCorrectionInfo().
ISignalSymbolModel: followed recent changes.
Demodulator: followed recent changes.
SignalBitModel: followed recent renaming (XIModulation), now uses IForwardErrorCorrectionInfo and removed crcCheck class.