Edit node class name prefix upon "Save/Move Composition to Node Library"

As it is the username that decides the prefix for stored nodes, mine gets unnecessary long, and editing them afterwards breaks the compositions. Added bonus is grouping by name (i.e. magneson.util.somenode.vuo) for different utilities and effects.

I’ve opened this feature request for voting (and modified the title).

Implemented in Vuo 2.0 beta.