* rewrite network protocol/service to use channels
* remove use of unwrap
* re-introduce with_spec
* remove unnecessary mut
* remove unused param
* improve with_spec, add with_gossip
* rename job to task
* style: re-add comma
* remove extra string allocs
* rename use of channel
* turn TODO into FIXME
* remove mut in match
* remove Self in new
* pass headers by value to network service
* remove network sender from service
* remove TODO
* better expect
* rationalize use of network sender in ondemand