2 breaking changes
* LevelHandler is now an interface. All instances where a LevelHandler is used in the core should now only
be using the LevelHandler class unless its classic specific.
* All IOClients now have a client type and can have the PacketManager filter out packets based on its client type.
This means that all future packets must specify which clients they support.
Merge branch 'master' of https://github.com/MCForge/MCForge-Core

Conflicts:
	src/net/mcforge/networking/packets/DynamicPacket.java
	src/net/mcforge/networking/packets/minecraft/Handshake.java
	src/net/mcforge/networking/packets/minecraft/KeepAlive.java