Replace Eigen regression

As we're migrating from Eigen to (Sca)LAPACK the LinearRegressor class should be updated first.

Currently it serves as both implementation of OLS and rigde regression as well as interface to Tadah.MLIP. The aim is to develop separate interface and move updated implementation into new classes.

changed milestone to %WP1 Improved parallelisation: speeding up Tadah!

New OLS and RR classes added to MODELS

marked this issue as related to #2 (closed)

closed