adding sendBitstream in NetioTxCore to send data using bytes instead of 32-bits words

NetioTxCore handles provides functions to send 32-bits words through the FIFO (although the underlying scheme uses bytes). However, as noticed by @ezhivun and @otoldaie an undesirable 0-padding is done by BitStream.Pack() that propagates to 32-bits words. The implemented solution adds a writeFifo function that sends bytes instead of 32-bits words and a sendBitstream wrapper.