Workshop: Stablish "Gradding mapping table" as required on Number of Errors Strategy

On the Workshop tool, we found confusing that "Grading mapping table" not to be required.

Scenario

1. We create a workshop instance without stablishing its "Grading mapping table".
2. We reach assesment phase and any students do their assesments. They obtain a grade based on the default mapping table (%), normally 100% not taking into account the actual YES/NO filled.
3. Then, the teacher stablish the actual "Grading mapping table", but the grading assesments are not recalculated automatically.
4. Each student has to get back to the assesment phase and to resend his/her perr assesments.

Improvement proposed

A) The simple way: "Grading mapping table" to be required avoiding these kind of problems.

B) The complex way: After changing the "Grading mapping table", every peer assesment must be, automatically, recalculated.