bring back rank update notifications
pros: all players benefit from more accurate instrumentation of match results, rank being second to victory when considering one's performance against previous performance. code was already written and working to PM rank adjustments following a match. the reported rank adjustment reflects the weighted odds and adjustment of the ranks competing and is unnavailable to the player in any other discrete capacity per match.
cons: sore losers and newbs mistake rank for something not-a-game and cause discomfort to others post-game. somehow that led to a snap decision to remove notifications and to round down rank in lobbies.
Related to #164 in that rank updates won't necessarily contain new information if we truncate them.
This should be easier to do now that we can more reliably track player changes.