Renamed some classes

ClientOutput to ClientPacket (names of all classes that extend ClientPacket now start with CP)
ClientInputHandler to ClientPacketHandler (names of all classes that extends ClientPacketHandler now start with CPH)
ServerOutput to ServerPacket (names of all classes that extend ServerPacket now start with SP)
ServerInputHandler to ServerPacketHandler (names of all classes that extend ServerPacketHandler now start with SPH)