Generate thumbnails in the library

[fmang]

Pictures are a nice way to find and remember songs when browsing beatmaps.

While it's easy to use the full size pictures, it's quite a burden on the browser to scale everything on the fly. Instead, oshu-library should pre-generate all the thumbnails first. ImageMagick provides an easy interface to do that.

Where to store them? When to delete the old ones? What about space management?

[lanodan]

Where to store them?

In ~/.thumbnails if it doesn’t create a conflict, otherwise probably something like ~/.cache.
I think the space-management could maybe done by having a command to delete maps.