Author: David Mudrák
MDL-72488 lang: Fix hard-coded English string at grades import form
Also adding a help tooltip as this seems to be the most important field
in the form and yet it was the only one without a help.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=c755938aa30c4edb6d230d020331b29988b40742
http://github.com/moodle/moodle/commit/c755938aa30c4edb6d230d020331b29988b40742
+ 3.10 en [importdata,core_grades]
+ 3.10 en [importdata_help,core_grades]