Add configuration option for administrators to restrict views available based on number of students in class

[jennlove-um]

Describe your problem or feature you'd like added

For small classes, maintaining student privacy becomes a concern with data visualizations. This becomes most important for the Grade Distribution visualization. In a small class, there is a risk that students could deduce an individual student's grade based on the histogram data.

Describe the solution you'd like

Provide a way for MyLA administrators to limit which views are available to be added to courses based on a minimum number of students in the course. For example, allow administrators to set a threshold of 11 students, indicating that courses with 11 or fewer students would not be able to enable Grade Distribution.

Describe any possible alternatives you've considered

Currently, institutions are making recommendations to instructors via documentation to let them know what minimum enrollment should be considered when turning on views. Adding an administrative configuration would allow institutions to enforce enrollment thresholds for the Grade Distribution view.

Further discussion may be needed to determine whether the threshold needs to apply to only the Grade Distribution view or if it should also apply to the Resources Accessed view.

[jennlove-um]

Tested in MyLA beta. The configuration works - the GD display can be restricted based on the number of students in the class.