Author: Jerome Mouneyrac
MDL-42081 EditPDF: Add default stamp images
http://git.moodle.org/gw?p=moodle.git;a=commit;h=7444cf322ee1c863dad7e52ec2b5e8ea7266b067
http://github.com/moodle/moodle/commit/7444cf322ee1c863dad7e52ec2b5e8ea7266b067
+ 2.6 en [stampsdesc,assignfeedback_editpdf]