Unified RateML
Created by: DeLaVlag
Hello @maedoc and @sdiazpier. This PR is about unifying the CUDA and Python RateMLs and using an unmodified Pylems which can be installed as a dependency. The interface of RateML is expanded with 2 arguments: language for generation and user can enter a location in which generated models are stored. Also XSD validation for XML files is added. For the CUDA models now also a BOLD kernel is generated. The two collabs featuring TVB and CUDA model generation + simulation are added to TVB demos folder.