provision/docker/scheduler.go: updating Unregister function comment
api/admin: creates function to register handles

Relates to #588
api/admin.go: creates function to run admin server

Relates to #588
etc: adds admin-listen default port configuration to all confs

Relates to #588
provision/docker/scheduler: change Register and Unregister params to attend ducler-cluster.Registrable interface
provision/docker/handlers: creates handler to add a node to segregate scheduler

Relates to #588
provision/docker/handlers: creates handler to remove a docker node

Relates to #588
provision/docker/handler.go: created helper function to unmarshal body

Relates to #588