[WIP] Feeds: Added ability to switch between next/previous pages.

# Do not merge

**To-dos:**
* Don't force "generic" parameter for parseEntries when clicking next/previous links
* Sort out "disabled" class logic (renamed to "disabled-no" for the moment to make testing feasible)
* Make clicking the next/previous links focus on the list instead of jumping to the top of the page
* Add better support for lazy loading of YouTube feed items (might be a longer-term item)

CC @thomasgohard 
@thomasgohard FYI the extra condition I added here messed up a lot of things that tie into how pagination buttons get shown. Before I added it in, new pagination links would get injected every time a next/previous button got clicked, which broke a lot of stuff. Added the extra condition as a quick-fix without realizing what it would do in practice. Gonna look into it before COB tomorrow.