World event system

Add: An event system that is based on Classmod and can be used by all kinds of world classes (Classmod classes that are located in the .world package or one of its subpackages).
Replace the old process event system with the new general one

Remove: The entire old process event system in .world.comp.program.event because it isn't used anymore.
Remove: The SEND_MESSAGE function from the Process class.
Add: Support for the new event system (.world.event) in the program executor class.
Add ReceivePacketEvent to replace the old PacketEvent

Add: The ReceivePacketEvent in the .world.comp.net package replaces the old PacketEvent that ran on the old ProcessEventSystem. The event can be used for notifying any listeners on arrivals of packets that are somehow related to them.