Minor changes for ghosts, added verb to remain anonymous

See commit messages for details.
After a brief discussion in IRC it's been made clear that the intended purpose is to clarify that the standard Ghost verb will announce the admin's presence to the dead chat. I'm awful at these things but perhaps this will work:
You have the ability to Admin-Ghost. The regular Ghost verb will announce your presence to dead chat. Both variants will allow you to return to your body using 'aghost'. What to you wish to do?