Author: Jamie Pratt
MDL-47494 ddimageortext: NOBUG added feedback for student when they have not dragged an image to each drop zone.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=9b2ccabae80e8ed8106a0deba2cd6bcce462909f
http://github.com/moodle/moodle/commit/9b2ccabae80e8ed8106a0deba2cd6bcce462909f
+ 3.0 en [pleasedraganimagetoeachdropregion,qtype_ddimagetoimage]