Send dispute resolution accepted notification to both parties

[jjeffryes]

Currently, when a dispute resolution is accepted by calling release_funds, the other party is not notified. The following should happen:

1. the buyer and seller should both receive a notification over webSockets of type "payment_released" with the order id of the order
2. when get_purchases and get_sales are called, the order should return a status of 6. Currently if the buyer wins, the buyer gets a status of 6 on the transaction, but the seller gets a status of 5, and doesn't know the resolution has been accepted.

Related client issue: OpenBazaar/OpenBazaar-Client#838

[cpacia]

I'm inclined not to do this now. It would need yet another network message that needs to make it to the other party, and would likely end up in the DHT adding to the amount of data in there.

[drwasho]

This is pretty important from a UX perspective. Is this something you have the bandwidth to do @cpacia ?