Create combined ranked leaderboard #31
Description
Average many ranked game leaderboards together to create a "global" ranked leaderboard. Each game should be weighted equally and averaged among its sub categories. Then all games are averaged.
If a player has not played a particular leaderboard, their ELO counts as 0 for that leaderboard.
MMR should also be calculated based on this combined ELO by either averaging MMR across leaderboards or decaying based on the least recent gamemode played.