Make it possible to send a transaction with multiple recipients and output values.

[nuttycom]

Is your feature request related to a problem? Please describe.

When I spend my ZEC at the coffee shop, I want to be able to both pay the vendor and tip the barista. It would be convenient to be able to do both at once by constructing a transaction with outputs for both of them.

Describe the solution you'd like

On the send screen, maybe there could be a little + button that allowed me to add another recipient with separate (address, amount, memo) fields for each successive recipient.

This could also be used for doing other things like manual note management (although that really would require being able to see the distribution of the notes in one's wallet, which we don't provide a way to observe.)