Send: fee transparency & ability to set fees

[dergigi]

Two things:

• It should be transparent how much a transaction is expected to cost in terms of fees feat: display fee settings on Send page #532
• Users should have the ability to manually set feat: basic fee settings #522

Keep in mind that, according to waxwing,

Joinmarket's design doesn't really allow the concept of 'try coinjoin with a small test amount' and then extrapolate to larger sizes. Such a large fee as you saw is unusual today, but very possible. With amounts in the thousands of dollars, percentage fees can instead be really negligible.

See also:

• Docs: Fees
• JoinMarket: A note on fees