Implement OUTPUT_BINARY

Implement OUTPUT_BINARY

This requires the PD to have a tuple in its class called 'binary',
which contains a list of strings describing the different binary
classes it can output. For the SPI decoder this might be 'MOSI' and
'MISO', for example.

The data is submitted to the frontend as struct srd_proto_data_binary,
which contains the class that data belongs to.