* swarm: completed 1st phase of swap accounting

* swarm: swap accounting for swarm with p2p accounting

* swarm/swap: addressed PR comments

* swarm/swap: ignore ErrNotFound on stateStore.Get()

* swarm/swap: GetPeerBalance test; add TODO for chequebook API check

* swarm/network/stream: fix NewRegistry calls with new arguments

* swarm/swap: address @justelad's PR comments