library: optimize folder thumbnailer so we don't need to re-create the split imagery on every draw event. add support for retina displays

library: unify string representation of albums (& tracks) and shows (& episodes) on iOS 6 and 7 (close #10190)

Fix a rendering issue where fetched and available artwork may disappear over time

Deploy NSByteCountFormatter instead of calculating file sizes ourselves as this results in a more appealing appearance

Fixes missing / incorrect artwork, improves labelling

library view on pad: leverage MLKit to show a show episode's show name within the thumbnail and just the episode name as item name; same for audio-only media if artist and album name are known

Screenshot here: http://cl.ly/image/3A051P3a403h