verification and extension of Deming regression

[wptmdoorn]

• verify new implementation of Deming regression
• extend Deming regression with its weighted
  https://analyse-it.com/products/method-validation/deming-regression.
  Estimation of the Linear Relationship between the Measurements of Two Methods with Proportional Errors. Kristian Linnet, Statistics in Medicine Vol 9 1990; 1463-1473