Refactor Course/Pathway Filtering

[EvWhymark]

The course and pathway filtering is a mess. It is hard to read and understand what is happening. I am under the belief that we should move as much of the filtering outside of the API and do that within the website. And after moving it outside of the API we should also probably go through and make the code more readable. This should mostly be done via redoing how the code currently works and most importantly adding comments.