Define a default for rights['public'] in views/models/base.py. Alter rights
in views/models/site.py to allow anyone, even signed-out users, to view the
site home page.
Patch by: Todd Larsen
Hide the 'scope' property from forms for now, since this is really supposed
to be set by "Role context" as determined by logic code in the controller.
Patch by: Todd Larsen