Description for error characteristic curve view should link to paper

[gkronber]

The error characteristics curve view for regression models should have a link to the paper:

Bi, J., & Bennett, K. P. (2003). Regression error characteristic curves. In Proceedings of the 20th international conference on machine learning (ICML-03) (pp. 43-50). https://www.aaai.org/Papers/ICML/2003/ICML03-009.pdf

Additionally, we could think about changing the implementation slightly to match the description in the paper.