Fixes #7465: display message when there aren't any subscriptions.

http://projects.theforeman.org/issues/7465
fixes #7422 - documenting the `label` param for env creation, BZ 883170
Merge pull request #4665 from komidore64/rmi7422-label-on-env-create

fixes #7422 - documenting the `label` param for env creation, BZ 883170
Merge pull request #4667 from waldenraines/7465

Fixes #7465: display message when there aren't any subscriptions.
Fixes #7446/bz1140653 - Host delete dynflowed

Previously when a host got deleted in foreman either via UI or API
the content_host active record would get deleted but NOT the backend
like candlepin or pulp consumer information. This commit aims to fix that
by making foreman's delete host call use katello's consumer delete dynflow.