Implemented authID get method
Added unmarshall warnings

packethandler.Unmarshall now gracefully handles failure to decode a
packet and prints an error.
AuthAccept improvements

Implemented a decode method for the AuthAccept packet
AuthReject improvements

Implemented a decode method for the AuthReject packet
AuthRequest bugfix

Fixed a bug where AuthRequest.Encode() was not encoding its own packet
ID, preventing it from being decoded correctly.