Try out a new way of regrouping albums in the playlist. As of rigth now it is not much faster than the old one, but as it does not requre regrouping of the entire playlist in most cases, it has potential tp become a lot faster if the internal datatypes are optimised (such as using hashes instead of lists).

Grouping seems to work correctly, but there are still some issues with redrawing the playlist leaving some thing looking slightly broken untill a redraw is triggered.

This grouping aproach also has the advantage that information about collapsed groups are not disarded every time a regroup is triggered. Oh, one more thing, removing single items from the playlist seems to send it into some kind of an infinite loop at the moment...