Drop-in comm and comm slow down

PART I
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.

PART II
Slows down comm. (Cherry-picked Daniel's commit.) New rules make explicit how many packets we can send per second. Initial testing suggests sending less packets may actually have positive effect on wireless performance.