Remove control channel and CLI

strong-cluster-control is now only a cluster wrapper, run-time control
is being moved to strong-supervisor, including control channel and CLI.

The easy part of https://strongloop.atlassian.net/browse/SLN-1112

/cc @crandmck, don't make any changes yet, but please take note.

Merging awaits re-implementation of cluster control in strong-supervisor.