NSLog->DDLog, fix bug re. missing file segfault, comment out debug
Fix ARC warning re. retain cycles
Instant file/dir update
Make function for resetting attribute cache
In managed objects use assigned context
Pruning of empty artists/albums upon instant change
Use object's own managedobjectcontext
Library and LibraryView use separate CoreData contexts
Run Library on another thread
Fix crash where library is being updated as it's being refreshed