Adds super simple User roles and rudimentary dashboard.

The User model now supports 3 basic roles for distinguishing between
regular users and administrators, with a distinction between admins
that have access to everything and those that can only access tickets.

Admins access the Tickets via the dashboard scope. The controller and
views underlying the regular users' access to the Tickets resource are the
same ones used for the admin view (literally the same things shared bewteween
them, not identical *copies*). I want to have all admin access to the system
scoped at the url/path level but don't want to have seperate controller &
view stacks for them as there would be too much duplicated code there.
To make this work the Ticket model assumes responsibility for
retrieving the ticket(s) appropriate for the User to access based on
his/her role at the controller level, and divergent functionality in the views
will be exposed based on the User's role.