Add storage of captimes and fastest caps.

Add storage of captimes and fastest caps.

Fastest caps are recorded on a per-player basis in the game_stats
table, and the player's overall fastest cap on a given map is
stored in a new table, player_map_captimes.

One weird thing is if the constraint on game_id in the captimes
table is enabled, sqla throws an integrity error. For this reason
the constraint is disabled (commented out in xonstatdb) even though
it should be there. More investigation is needed.