LearnerND scale output values before computing loss

Closes #78 (closed)

In a way similar to the Learner1D

Recompute all losses when the scale increases with a factor 1.1.

My simple measurements indicate that with the ring_of_fire as test function the learner slows down approximately 10%. But we get in return that we scale everything to equivalent sizes before computing the loss.

TODO:

• Add some test(s).