write I/O interface

[Doralitze]

• [x] write input data structure
• [x] link input data structure with filters or use input filter, see also issue #4
• [x] implement io protobuf messages
• [x] write main bord driver based on libftdi and interface with FT600 chip on mainbord
• [x] Write Mackie Control Driver (Start point: http://www.midibox.org/dokuwiki/doku.php?id=mc_protocol_mappings)
• [x] Use libusb with libev (Start point: https://stackoverflow.com/questions/5852742/how-to-use-libusb-with-libevent)

[Doralitze]

Once we tested the full integration we might consider this one done.

[Doralitze]

Done.