Restore link to project description editing page
Clean up project roster editing page
Tweak validation/deletion of ProjectRole objects

1. The "role" attribute (name of the role) now has a unique restraint.
2. When a role is deleted, its corresponding group is as well.
Formset for editing project roles
View for editing project roles

This is a little hacky-- I'm doing in javascript what I should be doing
in Django: iterating through the checkboxes in the formset and
constructing a form with swapped x and y axes. This is necessary because
support for iterating through a ModelMultipleChoiceField was only added
in Django 1.6. Once we upgrade, we should change that. Until then, this
is ok, though.
Add breadcrumb to roster/role form pages
Fix "Featured items" page

First, fix the deprecated call to user.get_profile() in the
change_featured_items view, updating it to use our newer auth APIs.

Second, fix the generic JS function for searching arbitrary models.