MDL-47713 Grades: Change contribution column to a percent of grademax
MDL-47713 Grades: Update all the behat tests to use % in contribution column
Merge branch 'MDL-47713-master' of git://github.com/damyon/moodle
MDL-47763 Grades: Handle the case when a grade category is hidden.

This was breaking the contribution column, which needs to know the
weights of all the categories up the tree, whether they are visible or
not.