supervisorctl: add command-line options as module parameters

Adds more parameters which may be passed to supervisorctl:  config,
serverurl, username, password

Also refactored the various `module.run_command(build_a_string)` calls
into a single `run_supervisorctl` function.
supervisor_ctl: rename to server_url and improve documentation
Merge pull request #3442 from neomantra/supervisorctl

supervisorctl: add command-line options as module parameters