add new process in supervisor state

process is added if it wasn't there before

some nice supervisor modules included:
 * supervisor.{add,remove,reread,update}
 * supervisor.list - list all process states
 * supervisor.custom - run any custom command (eg from plugins)
do not collide with builtin name ``list``

it was really just a fancier formatted status anyway
forgotten doc string
Merge pull request #3375 from kvbik/more-supervisor-funcionality

add new process in supervisor state