Allow prereqs of overridden course to count for major

[theRoughCode]

Is your feature request related to a problem? Please describe.

Let's say someone comes to university with a substantial background in pure mathematics. They override into PMATH451 in their 1A term, thereby bypassing all calculus requirements for their program in addition to many others. In this case, all courses on the prerequisite chain should be ticked off. (Refer to below)

Additional context #125