improvement on addBulkAction function.

It takes into consideration  the $config values passed as function parameters.

code/GridFieldBulkManager.php

@@ -211,9 +211,9 @@ class GridFieldBulkManager implements GridField_HTMLProvider, GridField_ColumnPr
 		}
 		else{
 			$config = array(
-        'isAjax'        => true,
-        'icon'          => 'accept',
-        'isDestructive' => false
+				'isAjax'        => isset($config['isAjax']) ? $config['isAjax'] : true,
+				'icon'          => isset($config['icon']) ? $config['icon'] : 'accept',
+				'isDestructive' => isset($config['isDestructive']) ? $config['isDestructive'] : false
 			);
 		}
 
@@ -379,4 +379,4 @@ class GridFieldBulkManager implements GridField_HTMLProvider, GridField_ColumnPr
 
 		user_error("Unable to find matching bulk action handler for ".$request->remaining().'.', E_USER_ERROR);
 	}
-}
+}