Created Users Index and moved Create User into logged in area

Now, users can only be created after they are logged in. Permissions
and restrictions still have to be implemented (eg. students can't
create users). Since users are now created within a logged in area,
the user is no longer logged in after "they are created"

I have also created a users index, which currently displays full
name, display name, and user type. The list is also sorted by last
name. More can be done, such as accessing users/edit (admins),
searchin in specific columns instead of all.
Added pagination, sorting, and permissions for users index

Pagination and sorting has been implemented for users index. I have
also added restriction to the users index for admins. Due to this
I have to put the users index in its own controller. The Users
Controller has to be accessible by instructors. If we keep the
two pages together in the same controller, teachers and students
will be rejected from create user form.

I have also implemented Flash messages using a library found online.
More information can be found at https://github.com/gtramontina/angular-flash.

Work that still needs to be done include changing all success and
error messages into flash messages and fixing invalid property
error for ngTables. Some permissions modifications also has to be
done (including students can't create users).