`remote`-helper

[gbraad]

allow 'any' app to work remotely, such as

• remote [host] screen
• remote [host] app <appname> ..., uses rshell/rdot
• remote [host] playbook ..., remote [host] action ..., ... remote_action, remote_notebook, similar to remote_playbook #203
• etc.

refactor or rdot, rscreen, ...