[Improvement] Notification when sending IOU triggering DEX to XRP

[WietseWind]

Right now, when sending a non XRP currency (IOU), this will trigger either:

• XRP » XRP
• IOU » XRP
• IOU » Same IOU

If the destination has the same IOU we will send the IOU as partial payment. If the destination doesn't have the same IOU setup, we auto convert using DEX to XRP. We must inform users that this will happen.

We should confirm the currency to SEND as well, the value entered is the amount picked to SEND

Suggestion:
[Currency]
EUR - Euro
Balance ...
Note: the recipient cannot receive **Euro**, so XRP will be delivered.

Amount:
€ (if icon, else EUR) 1

[WietseWind]

@thisistriss for visual review

[WietseWind]

May upgrade in a future version based on #108

[WietseWind]

We decided to remove this in 1.1