Improve file upload UX

Fix incorrect highlight logic

Fix transition on fileupload highlight

Handle drag leave

Fix draghover

Minor style improvements

tpl/page.php

@@ -254,6 +254,13 @@ if ($DISCUSSION):
 		</div>
 <?php
 endif;
+?>
+<?php
+if ($FILEUPLOAD):
+?>
+		<div id="dropzone" class="hidden" tabindex="-1" aria-hidden="true"></div>
+<?php
+endif;
 ?>
 		<section class="container">
 			<div id="noscript" role="alert" class="nonworking alert alert-info noscript-hide"><span class="glyphicon glyphicon-exclamation-sign" aria-hidden="true">