Limits Participad Settings access to Super Admins
Because Participad as installed on thatcamp.org requires certain settings, it seems wise to remove the Participad Settings menu for site administrators. The sample.thatcamp.org site currently has Participad activated with the proper settings, so new THATCamp sites - which are replicated from the sample site - will have the correct settings, and these should not be altered. This commit also makes minor style tweaks to the front-end Participad widgets.