Pass publisher instead of amqp_client into VumiApi.from_config_async().
Clean up command and event publishers and remove unnecessary configuration.
Merge branch 'develop' into feature/issue-932-better-VumiApi-publisher-setup

Conflicts:
	go/vumitools/app_worker.py
Merge branch 'develop' into feature/issue-932-better-VumiApi-publisher-setup
Merge branch 'feature/issue-932-better-VumiApi-publisher-setup' into feature/issue-915-metrics-api

Conflicts:
	go/vumitools/app_worker.py