Modified mahara.php and lib.php so that when
 a user with an expired account tries to log in
they are told 'Sorry, your account has expired.
You can contact the site administrator to have
the account reactivated,' with a link to the
'Contact Us' page.

Change-Id: I6b461d40e37a88ac513649a1d4a6d83c5d3711a4
Signed-off-by: Ali Kaye <alexandrakaye.student@wegc.school.nz>