Support for courses with variable units

[ecxyzzy]

Before #351, courses with variable units are displayed as having only the minimum number of units; for instance, COMPSCI 199 can be counted for 2-5 units, but the courses view and Peter's Roadmap show that it fulfills only 2 units. #351 shows the unit range if a course has minUnits != maxUnits, but it will still fulfill only the minimum number of units in Peter's Roadmap since I'm not sure how best to proceed with such a change.