Autogroup settings change

[Dirk Hohndel]

I just committed another change that had been on my todo list since
forever. The autogroup settings were criminally insanely stupid. Having
that twice (preferences and menu) and having different semantics for
when a change would be saved in the config was just nuts. And saving it
in the config was a mistake to begin with. This is much more a per file
feature.

Please take a look.

/D