Working on creating a more exchange-like UX for agora. Incremental improvement here.
- Often, the spot price offer is not buyable. This happens for example on FIRMA where the lowest offer could have a min buy of $98. So a user without $98 will see this as unbuyable, and may think no offers are buyable.
-> So, we hide such offers from such users.
- We add 25% / 50% / 75% / max buttons to quick select a buy amount for available offers. In a real exchange, this would always be relative to the user's stack, and it would accept (maybe) multiple candles. We can get there, but I think we need better ecash-wallet logic to handle that properly. For now, apply these to a single candle. If the user can afford the whole offer, then the %s apply to that offer. If the user cannot afford the whole offer, then the %s apply to the user's balance of XEC.
Note that we DO NOT (yet) account for tx fees in these calculations. This is pretty complex and, if it proves necessary (perhaps the token qty quanta requirements make fee errors rare) -- we will add it, but should be in its own diff.

