Add an event to catch players sending a hat message

This adds a hook to EntityPlayerSP#sendChatMessage which allows mods to cancel a chat message message from being sent, modifying, or just inspecting it. I'm 99% sure I edited the base class incorrectly, my apologizes. 

I also just realized that line 32 of EntityPlayerSP should be 
this.sendQueue.addToSendQueue(new C01PacketChatMessage(evt.message));

Again, my apologizes. 
http://pastebin.com/TSrnueuQ