Get rid of ObjectIO

[choll]

This was done for the uni project, it would be better to do something like:

1. Helper opens and configures the BPF file descriptor
2. Passes it to the GUI over local domain socket
3. GUI runs a thread which reads from the socket into NSData objects or Packets and puts them onto a queue
4. GUI main thread takes NSData/Packets off the queue and displays them.

Decoders would then just point into the NSData object held by the Packet.

Upside: Faster (serialize/deserialize to socket is eliminated) and use less memory (Decoders just point into packet data) than the current design.

Downside: Privilege separation is more or less removed, but that problem can be better solved by writing decoders using the Python plugin architecture anyway.

[choll]

Might be a good idea to use pcap instead of bpf, if it would be less code