filebrowser: jade for filter.html

vispa/extensions/file/static/html/filter.html

+
 <div class="filterField">
-    <input type="text" class="form-control" placeholder="Filter files">
+  <input type="text" placeholder="Filter files" class="form-control"/>
 </div>
\ No newline at end of file

vispa/extensions/file/static/html/filter.jade

+.filterField
+    input.form-control(type="text" placeholder="Filter files")