That was a really tough decision, but it was done after the
following tries:

1) I need to embed KoFillConfigWidget into KoStrokeConfigWidget
2) But KoFillConfigWidget depends on KisStopGradientEditor, which
   depends on:
       - KisDoubleSliderSpinBox (depends on KisPart)
       - KisColorButton (depends on a lot of stuff in KisInternalColorSelector)

So as a result I just decided to move KoStrokeConfigWidget and all its
dependees higher in the hierarchy :(

I hope some time in the future we will be able to move these classes back
into flake...