Add first version of Eddy Viscosity (EV) model implementation for PyWake

This merge request includes an implementation of the Eddy Viscosity (EV) model for PyWake developed by Christian Jonsson and Alistair Merry (both at Natural Power at the time and both now at KUDO Software).

This merge request was originally created in March 2023. Minor refinements have been made since then, and it has been kept up-to-date with the master branch. The implementation has been tested by several organisations with positive feedback.

Thanks to Olivia Bentley and Steve Cordle at BrightWind for pointing out the need to handle zero values in the wind speed inputs when scaling the turbulence intensity inputs.