(LearnerND) fix plotting of scaled domains

When a domain is huge, only one interpolated thingy is drawn. We should:

1. take some minimum
2. scale volume with the size of the domain

created branch 128-learnernd-fix-plotting-of-scaled-domains

mentioned in merge request !140 (merged)

closed via merge request !140 (merged)

mentioned in issue #125 (closed)