Rarities for cards in sets (close #1532):

• Sets can optionally define rarities (common, uncommon, rare) for cards in that set. Either all cards or no cards in a given set can have rarities.
• Rarities affect only the Set Draft format – they determine how often cards come up (on avg: 3 rare cards, 7 uncommon cards, 20 common cards per drafted deck of 30)
• Cards display their rarities only when viewing/editing a set with rarities or drafting/playing in the Set Draft format
• Corresponding documentation and validation (sets with card rarities enabled must have ≥4 cards of each rarity)

Bug fixes unrelated to card rarities:

• fix Set being edited doesn't actually get loaded when refreshing a /set/[...] page #1656
• fix Deck name doesn't load when refreshing a /deck/[...] edit page #1657
• fix Flavor text on cards doesn't get saved correctly #1658
• fix Flavor text on cards doesn't display in CardGrid view #1659
• fix Flavor text on cards doesn't load when editing a card with flavor text in the Workshop #1660
• fix Rendered cards overflow slightly (in the stats area) when viewed at scale<1 (i.e. in set summary view) #1661
• fix Make flavor text on cards easier to read (toggle rather than tooltip) #1662
• fix Aborting a set draft by refreshing a page doesn't abort it for the other player #1663
• fix Aborted/forfeited games don't log a message in the game log about the abort/forfeit #1664
• fix "Preview" in the Workshop text blends into buttons above it at smaller screen widths (<1250px) #1665
• fix Increase minimum set size from 15 to 20 #1667