Add template for single user mode message

core/templates/singleuser.user.php

+<ul>
+	<li class='update'>
+		<?php p($l->t('This ownCloud instance is currently in single user mode.')) ?><br /><br />
+		<?php p($l->t('This means only administrators can use the instance.')) ?><br /><br />
+		<?php p($l->t('Contact your system administrator if this message persists or appeared unexpectedly.')) ?>
+		<br /><br />
+		<?php p($l->t('Thank you for your patience.')); ?><br /><br />
+		<a class="button" <?php print_unescaped(OC_User::getLogoutAttribute()); ?>><?php p($l->t('Log out')); ?></a>
+	</li>
+</ul>