[Patch] "No grouping" checkbox in playlist layout

[Nikolaj Hald Nielsen]

> Cool, I will try it out asap.

Except for a small compile issue witha debug statement somewhere, it
works great and I just pushed the entire thing + build fix to master!

Thanks! :-)

If you have not already done so, you should add your copyright to the
file you have changed and add yourself to the "thanks to" section in
main.cpp or app.cpp (I forget which one.... )

- Nikolaj