Specify Fee Payment Between Parties

[nkohen]

As discussed here, fees are currently paid evenly between parties in the funding transaction, when in reality each party should be paying the fees for the weight they contribute in their funding inputs, change output, and payout output (with the rest of the weight distributed evenly between them).

This is a non-trivial change as it requires parties to specify expected weights of witnesses to funding inputs during contract negotiation (to allow for deterministic funding transaction computation). This will require a mechanism similar to the currently proposed input_info type in the dual funded channel initiative. This complexity is why I've decided not to include this part of the specification immediately so that this can be handled on its own and with care, while making the specification easier to meet for now.

[nkohen]

closed by #81