BIP21: Pair created payment to newly received payments

[erdemyerebasmaz]

Re: #428 (review)

Example app currently uses a placeholder logic for tracking payments, due to a regression caused by ongoing changes on BIP21 support.

This logic should be updated after necessary information is added to Payment and/or ReceivePaymentResponse on:

• Send/Receive: Add BIP21 support #414

[dangeross]

Just looking at this briefly, we don't store the BIP21 when receiving (no tx yet), so the BIP21 is not set as the destination. An option would be to persist/sync addresses/BIP21s used to create payments, then lookup this info when creating the payment tx data for a pending/completed payment.