Changes

This is mainly a bugfix release. A large number of bugs have been eliminated including [https://gna.org/bugs/?5977 bug #5977], [https://gna.org/bugs/?6288 bug #6288], [https://gna.org/bugs/?6383 bug #6383], [https://gna.org/bugs/?5806 bug #5806], [https://gna.org/bugs/?6384 bug #6384], [https://gna.org/bugs/?6388 bug #6388], [https://gna.org/bugs/?6389 bug #6389], and [https://gna.org/bugs/?5746 bug #5746]. These are described in more detail below. To fix a few of these bugs large disruptive changes were required. This included the change of the local τ_m parameter name from 'tm' to 'local_tm' and the simplification of the [http://www.nmr-relax.com/api/1.2/specific_fns.model_free.Model_free-class.html#model_statistics model-free model_statistics() function ] and modification of the [http://www.nmr-relax.com/api/1.2/specific_fns.model_free.Model_free-class.html model-free calculate() function]. Therefore regressions and new bugs may appear in this release, most likely when the local τ_m parameter is encountered or during model selection.