This bug was reported by Sebastien Morin (https://gna.org/users/semor).
The problem was that the 'model_selection()' user function was incorrectly copying the data into the
model selection run when the local tm global diffusion model was selected over the sphere, spheroid,
ellipsoid, etc. The local tm global diffusion model was being treated as a single spin system model
by the 'self.duplicate_data()' function of 'specific_fns/model_free.py' and hence only the data from
the first spin was being duplicated. By passing the 'global_data' flag in from the model selection
code, the data duplication function is now acting correctly.
