Added the model, its description, the equations for the analytic models, and all references to the relax_disp.select_model user function front end.
sr #3154: (https://gna.org/support/?3154) Implementation of Baldwin (2014) B14 model - 2-site exact solution model for all time scales.
This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax##The_relax_disp.select_model_user_function_front_end
