[Leagues] Curated grouping of replays

[rjackson]

Add tabs to the league view to group games together however we may wish - to aid navigation/discoverability for leagues with 50,000 games

For example, for TI4 we can split the league page into:

• American Qualifiers
• SEA Qualifiers
• China Qualifiers
• European Qualifiers
• Play-offs
• Solo championship
• All-star matches
• Main event

Should probably have the ability to manage these relationships manually, or infer the relationships via filters (date range [qualifiers, play-offs, main event], player count [solo championships], team-complete bool [main event versus all star matches]).

[rjackson]

Automatic filtering now implemented with 49d14bc

Remaining tasks:

• Manual database-group relationships (for w/e reason)
• Web admin for the filters.