I also added two more things to Scrape, .65 strength and enable size/
pressure. With the old defaults the strength of the brush was
inconsistent with other brushes like clay strips. We should probably try
to unify the strength value in all brushes hardcoding the values
internally and set the interaface to 0.5 strength by default.

The texture and feather options are not in this patch because they are
not part of the brush data.