Improve support for inclusion-based group therapy

If pushing into a classroom to see a single student, you can simply select the "Individual" delivery model, and the engine will do the rest.  No problem.

If you wish to push in to see multiple students in the same classroom, there's no clean way to do this:

• If you specify the "Individual" delivery model, then the scheduler won't account for the fact that you'll be servicing multiple students at the same time.
• If you specify the "Group" or "Unspecified" delivery models, then it's possible that the scheduler will group students together who are from different primary classrooms.

This could be implemented as a single checkbox for inclusion.  When the box is checked and the "Individual" delivery model is not selected, the engine should ensure that all students in the session are in the same primary classroom.