Added the test j4 eclipse build target (build with 4 cores)
Added a standard implementation of broadcast in the AbstractNetworkInterface
The NetworkInterface implementations are now responsible for deleting the packets when they have processed them.
Wrote the first tests for the ReliableNetworkInterface.

Complete acknowledgment logic is not completely implemented yet
Implemented much of the logic of ReliableNetworkInterface.

A big part is still missing: the ack timers and packet retransmission.