Added concepts for "course equivalency"

When a school does major course revisions, students sometimes "straddle" the old curriculum and the new curriculum. Often, credits earned under the old curriculum can be applied to courses in the revised curriculum. Having a mapping between the two can ensure that admin staff can correctly and easily counsel students who are in that situation. These tables help with planning that mapping ahead of time.

Additionally, there are times when courses outside the school are granted general equivalency inside the school's course grid. These can also be mapped for future reference.