Git commits in Moodle 2.7.0 by Jonathan Champ

commit 643e341cc0777ce5296e51950c6bfb231b7fe4cd
Author: Jonathan Champ <jonathan_champ@ncsu.edu>
Date:   Thu, 20 Mar 2014 23:04:41 +0800
Tag:    v2.7.0-beta

MDL-29572 Grade Import: Avoid creating invalid temporary rows; Provide feedback on error