permission api should be clearer+discussion

I needed to change the read permission from the console, and I struggled to figure out how to do it.
self.permissions = ...   ?? do you have to set all of them?  set_reader?   Not to be arrogant but if it causes *me* this much trouble that's a very bad sign.  --LWH

I think there was a simple way to do it, but I would need to document that.

  --Ethan McCutchen.....Wed Dec 10 14:11:26 -0800 2008

  --Ethan McCutchen.....Thu Apr 30 10:04:41 -0700 2009

excellent.

  --Lewis Hoffman.....Thu May 28 11:26:54 -0700 2009