Time Out Outbound Payment Retires instead of Count-Out

[TheBlueMatt]

Currently we limit outbound payment retires to a fixed, configurable number. This is cool, but users think in terms of time, not retry counts. We should also add the option to configure a time spent retrying a payment before giving up.

[kafaichoi]

I would like to give this a try. Just want to flag it here to avoid duplicated effort from others:)