Higher max thumbnail size (Library)

[ChameleonScales]

Right now album covers are resized inside a portrait-mode rectangle with a fixed aspect ratio (0.67 ?). At max cover size ("500"px, notice the quotes), an album cover in landscape-mode will be shrunk to much less than 500px. On modern screens it starts to get small. 3 ways to solve this :

• simple way 1 : increase the max size
• simple way 2 : allow for custom aspect ratio
• less simple way : adaptive aspect ratio

I think the most elegant is option 3 but any other is fine.