Notes/TODO.
Removed unused variable.
Move listing_list to its own file.
Parsers now call back when they find a new node in a listing.

This means that class doesn't have to know about a lot of types. Also allows moving of the best-alternative-chosing logic into listing, which is more appropriate.
Remove pointless static ctor and finaliser.
Remove last traces of direntry_cache, because wtf.