Filtering performance optimisations

Cleaned up a whole bunch of things.

Code optimisations here and there (less vars where they weren't needed), manually (ugh) sorted and sanitised (lowercased and removed all non-word chars) the DLC list, converted DLC list var from array to object so that lookups are now close to constant time, fixed a weird bug with library filtering, probably some other small things that I'm forgetting right now.