Canfield-Staging -> production

- Implemented version 1 of the network system
    * It is currently limited to two players, and the server blocks until it receives a connection request from a client
    * Tank movement and bullet creation are currently sent across the network (plus one "Hello from Server" message). More to come.
- Textures are now preloaded, to eliminate hiccups that occur when a sprite type is loaded for the first time
- Resolved all warnings in the application code (i.e., the non-test code)
- Added Apache Commons IO library (because I wanted the NullOutputStream for network tests)
- Added two new integration tests: NetClientTestApplication and NetServerTestApplication
- Fixed bug in TankCameraController when the game map is smaller than the size of the camera (though this situation shouldn't happen in the real game)

Network.startServer() does not have an associated unit test, since it blocks when called. I've asked the team for an exception to be made in this instance. Network.connect does have a unit test, but it will fail if you don't have a network connection (it connects to localhost). I'm not convinced that having a unit test for this makes much sense, due to its reliance on heavy external resources, but its required by our rules, so I included it.