Make events more consistent and add missing register methods

[DanyGames2014]

• Renamed EntityRegister to EntityRegisterEvent
• Added a KeyBindingRegisterEvent.register method
• Added a BlockEntityRendererRegisterEvent.register method
• Added a BlockEntityRegisterEvent.register overload using Identifier
• Added a EntityRegisterEvent.register overload using Identifier
• Added a PacketRegisterEvent.register method which accepts PacketType
• Unified some events to use the Identifier, <register object> order in the register methods in accordance to register methods already using Identifiers.

It might be worth considering removing the String id register methods completely from stuff like entities and block entities

The funciton of the packet type registering tested using a an added test mod packet, everything else is pretty much helper methods