Fix fixture instruction
Show/edit positions on person page
Define basic abilities and add user_roles views

A normal user should now only see data and actions relevant to him.
A normal user won't be able to access any other person's data.
New user_roles views/controller have saner semantics than
pseudo-resourceful roles_controller.  Fixed up a couple places that
weren't properly checking ability.
Keep User and Person email in sync
Schedule display tweaks
More clarity for the logged-out user.