JS: Results/marking view + annotations

This PR includes JS updates for files relevant to the results/marking view. This includes the SourceCodeGlower, used for displaying the code and for highlighting the annotated lines, and the file picker (the <-, -> buttons and the select dropdown).

Prototype has been converted to jQuery or vanilla JS.

This includes changes/fixes for PR https://github.com/MarkUsProject/Markus/pull/1244.
I just realized I haven't finished converting this file from Prototype yet (likely because I was looking for a replacement for the `$R` object). It's likely that I'll be using regular `for` loops to iterate over things instead of using `each` (jQuery) or `forEach` (JavaScript) since it's faster.