wire up payments - outlays NOT updated

[gudnuf]

This enables prisms to be payed out, but only when nothing goes wrong. There is still plenty of error handling and refactoring to be done!

Notable changes:

• I moved all functionality of paying a prism to the Prism.pay() class method

  • This means that both the payment triggers (invoice_payment and executepayout) use .pay()

• Prism payouts get triggered by payment of an invoice (bolt11 or bolt12 generated)

• made sure to delete BOLT11 bindings when the payment completes

• prism-create now returns as a dict, not json. This makes it easier to parse the response.

[farscapian]

Tested and verified. Things looking good.