Add Dash to Edge Payment Protocol so Anypay Users Can Pay with Edge

[derrickhorton]

This issue will be cross-posted to Edge Wallet's GitHub. The issue is that Edge accidentally removed support for Dash with the Payment Protocol. However, this is possible to re-implement using their open source code.

The goal is to re-activate Payment Protocol on Edge Wallet for Dash. (It worked before, but seems to be turned off or overlooked.)