Labtool uses too much of memory on courses with lots of students

[mjaakko]

This is probably caused by components receiving unnecessary data as a prop which creates a lot of copies in memory.

Related to #941

[mjaakko]

This might be too difficult to solve properly. Currently Labtool fetches all data from one course (this could be at least few megabytes for courses with lots of students) and passes that as a prop to many React components. We could filter that data to pass only what is needed as a prop, but proper fix would be to fetch only data that is needed from the backend and this would require rewriting most of current code.