TVB-2563 Adjust Zerlaut models
Created by: liadomide
Migrate changes from tvb-library into tvb-root repo. Basically changes from here https://github.com/the-virtual-brain/tvb-library/pull/91 are copied into tvb-root We should see how this new model code behaves in Phase Plane and Simulator and aftrwards merge. We now even have a working example in a notebook