Drop-in comm

Comm system for the drop-in challenge. Sends an SPLStandardMessage, instead of a proto. Puts the proto in the extra data field, so changes to the proto should not require any changes to comm. 

USE_SPL_COMM flag should be set to true when we are playing a drop-in game that way we fill world model proto with contents of SPLStandardMessage. USE_SPL_COMM should be false when we play a normal game.