Extract common utilities

[photm5]

This issue depends on #1.

• Server and supervisor both need the same message parsing and command framework
• Server, visualizer, and sniffer all need a TCP accept loop

[photm5]

I decided on combining all the seperate cabal projects into one, but leaving the executables seperated.

[photm5]

Commit e85b598 merges in some nice things, but there are more things to extract. From the top of my head:

• Server and supervisor should have a way to wait for messages with a certain ID
• Sniffer and supervisor should reconnect when the connection is lost (See #6)