Minimum requirements improvements

[mjaakko]

• Minimum requirements should be visible on final review page before submitting review
• Final review should have a field for grade (which is always optional)
• Student list should have a column for grade (should be visible only if at least one student has grade)
• Minimum requirement checklist items should not specify points, but instead effect on grade (e.g. 2 -> max grade 3)
• Minimum requirements should be visible when creating review, for example by having a different section for minimum requirements or displaying an icon on minimum requirements.

This issue should be split into multiple smaller issues

[hisahi]

Make sure to include Grade in CSV

[hisahi]

Split into #1036, #1037, #1038, #1039