add reorder option to filter

Datagrid/Datagrid.php

@@ -159,6 +159,11 @@ class Datagrid implements DatagridInterface
         return $this->filters;
     }
 
+    public function reorderFilters(array $keys)
+    {
+        $this->filters = array_merge(array_flip($keys), $this->filters);
+    }
+
     /**
      * @return array
      */

Datagrid/DatagridMapper.php

@@ -110,4 +110,15 @@ class DatagridMapper
 
         return $this;
     }
+
+    /**
+     * @param array $keys field names
+     * @return \Sonata\AdminBundle\Datagrid\ListMapper
+     */
+    public function reorder(array $keys)
+    {
+        $this->datagrid->reorderFilters($keys);
+
+        return $this;
+    }
 }