Move GradientSteps data to GeoTexSvxGradient and adapt
interfaces. Also move tooling to more isolated place
in gradienttools in basegfx.
Keep everything still compatible, the work will be now
to adapt all six different derivations of
GeoTexSvxGradient to make use of the evtl. given
GradientSteps.
Change-Id: Iaa212763c603d46de0a94b1b203b979bb7ce359d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/147050
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>
ea1d3d11ca