Alias Role separation on Discographies

[Secret Squirrel]

Based on a suggestion by Cedile and Revoc, I've made a change on the artist discographies. Now, aliases are separated by role instead of just by album. This is mostly important for albums where an artist uses multiple aliases for different roles (or sometimes even the same roles, like on many Bemani albums).

This turned out to be more of a challenge than I thought, so please report any unusual or unexpected behavior.

Also, this might make some credits a little verbose, particularly if an artist with a lengthy alias has 4 roles on an album. If you find such a discography, please post the link here so that we can see if we need to make some adjustments.