Group icons by pack

[Aktimoose]

Instead of the order being entirely alphabetical regardless of pack, it would make sense if they were grouped by the resource pack that added them first before being ordered alphabetically. This would allow for icons to be named freely without needing to prepend something just for the sake of keeping them grouped together.

These separated groups of icons would still be on the same set of pages, this would just affect the way they're sorted.