- Fetch collections during library refreshes
 - Add bottom nav menu entry for collections (if library has collections)
 - Implement a screen to show all collections
 - Implement very basic "collection details" screen listing the items in a collection. Not currently using library sorting! Not showing any details
 - Probably plenty of bugs re: weird data types, but simple implementation working

…yback when offline

If a book isn't cached and the server can't be reached, hide play/pause and download/delete.

…ewing books offline).

Never disable local progress (it was preventing the status bar from updating).

Simplify (reverse) logic on showing play/pause and download/delete buttons