Add maker address to return the testnet funds

[holzeis]

The message below does not specify where the fund can be returned. A button return all funds would be nice.

[holzeis]

cc @bonomat

[da-kami]

I think it would be cool to add the ability to return the funds to the send on chain screen. (This is where I would expect it...).

I propose we add the address of the maker to the faucet screen, but additionally display a Return funds to faucet Button in the send on chain screen, that is only visible if the network is testnet or regtest.