Author: Jamie Pratt
MDL-47494 ddimageortext: NOBUG adding an alt tag to drag and drop background image
http://git.moodle.org/gw?p=moodle.git;a=commit;h=5f924369ce0619a8921a3cccd40b529ebede3894
http://github.com/moodle/moodle/commit/5f924369ce0619a8921a3cccd40b529ebede3894
+ 3.0 en [dropbackground,qtype_ddimageortext]