Figure out a way to make Balanced works with Billy

[fangpenlin]

Original posted here:
https://github.com/PoundPay/balanced/issues/300

As the design of Balanced API doesn't allow us to charge bank account cross marketplaces, explained in following diagram

Therefore, we will need a marketplace dedicated for invoicing, and have all marketplace owner customer and their funding instruments to be cloned to that marketplace like this.

The approach we will use is to emit events about adding funding instruments (and all necessary operations), then let the syncer subscribes to these events, and duplicate these records into our marketplace for invoicing.