UI: Variety of tweaks and bug fixes
Add artist list to UI and all_artists API call

- Changed "info" request arguments
- Made loading lists optional
- Added r4_active_list cookie
- Added all_artists API call
- Change listeners_current variable to current_listeners
- UI: fix searchlist sorting bug
- UI: add tabs to lists
- UI: move AlbumList code and prefs to new albumlist.js
- UI: use Mozilla's docCookies for cookie management
- UI: Add current listeners list
- Add current_listeners API call
- UI: Fix ErrorHandler crashing when no JSON presented