[Class statistics] Add a toggle so that the user can choose if they want to include substitutions in the courses list or not

[x] Add a toggle so that the user can choose whether substitutions are displayed or not
[x] Add a symbol for enrollments (these are already 0's in the Excel file). Use the same icons as in Completed courses of students
[x] Hover texts
- Grade if there is a grade
- Enrollment date if there is an active enrollment but no grade yet
- Otherwise no hover text
[x] Exported Excel file should reflect these changes
[x] Update the info box to reflect changes
[x] Consider the Total column when using the toggle
[x] Also: why do student number filter on the page and on the SortableTable produce different results? If I use the student number filter, substituted courses are not included, while with filter on the SortableTable they are

UniversityOfHelsinkiCS / oodikone