Add properties to exercises for external trainers

[enauj]

My idea would be to add properties to every exercises containing information about the needed data, programs, and especially focus group and time needed to complete the exercise in a workshop.

I think this is needed for trainers, who have not designed the exercise themselves, and maybe don't have the time to prepare everything thoroughly so they can plan their workshops more accurately.

We will probably need feedback on the length of time it takes to finish the exercise, so we should add the platform email address to under this property.