Dungeons: Add Phoenix Down Drops

[Aidorouge]

Can we be allowed to buy Phoenix Downs with Grand Company Seals? GC Seals are largely worthless to me now and I'd love to have something useful to stock

Same for Poetics. I would gladly buy Downs straight from a vendor rather than have to sell poetics items for gil and then go to another NPC to prep.

See, now THIS I can get behind because the only thing my GC seals go towards anymore are gamble boxes trying to get 1 last mount and 1 last minion. I won't say no to blowing a 80,000+ stack of GC seals on only 2-3 boxes while the rest get dumped into Phoenix Downs, however many it might be, until I hit cap on them.