MINOR: documenting my new method, correct a coding convention about whitespace

git-svn-id: svn://svn.silverstripe.com/silverstripe/open/modules/sapphire/trunk@64460 467b73ca-7a2a-4603-9d3b-597d59a354a9

forms/TableField.php

@@ -757,6 +757,12 @@ class TableField_Item extends TableListField_Item {
 		return $content;
 	}
 	
+	/**
+	 * Get the flag isAddRow of this item, 
+	 * to indicate if the item is that blank last row in the table which is not in the database
+	 * 
+	 * @return boolean
+	 */
 	function IsAddRow(){
 		return $this->isAddRow;
 	}