Adjust design of maintenance mode page

Signed-off-by: Jan-Christoph Borchardt <hey@jancborchardt.net>

core/css/guest.css

@@ -607,6 +607,10 @@ form #selectDbType label.ui-state-active {
 	width: initial;
 }
 
+.body-login-container p:not(:last-child) {
+    margin-bottom: 12px;
+}
+
 .warning.updateAnyways {
 	text-align: center;
 }

core/templates/update.user.php

@@ -1,8 +1,6 @@
-<ul>
-	<li class='update'>
-		<?php p($l->t('This %s instance is currently in maintenance mode, which may take a while.', array($theme->getName()))) ?><br><br>
-		<?php p($l->t('This page will refresh itself when the %s instance is available again.', array($theme->getName()))) ?><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>
-	</li>
-</ul>
+<div class="body-login-container">
+	<div class="icon-big icon-error-white"></div>
+	<h2><?php p($l->t('Maintenance mode', array($theme->getName()))) ?></h2>
+	<p><?php p($l->t('This %s instance is currently in maintenance mode, which may take a while.', array($theme->getName()))) ?> <?php p($l->t('This page will refresh itself when the instance is available again.')) ?></p>
+	<p><?php p($l->t('Contact your system administrator if this message persists or appeared unexpectedly.')) ?></p>
+</div>