MDL-47700 Grades: Sitewide overview report isn't visible in some cases

Showing a overview report rank sitewide isn't visible to student in same cases
MDL-47700 Grades: Fix incorrect config for overview report showrank
MDL-48042 Questions: Reset Calculated qtype comments on datasets

Reset back the modifications of Calculated qtype comments on datasets
    done by MDL-47224

Signed-off-by: Pierre Pichet <pichet.pierre@uqam.ca>
Merge branch 'MDL-48042_26' of git://github.com/ppichet/moodle into MOODLE_26_STABLE