relax SVN archive

Changed the sign of the delta_omega frequency for the ZQ data in the 'CR72' and 'MQ CR72' models.

General improvement for the optimisation of many target functions.

For those models which use the tau_CPMG value, this is now recalculated. This means that if a user
inputs truncated nu_CPMG values, these are corrected when calculating tau_CPMG so that full precision
values will be used for the optimisation.

Improvements for the 'CR72' and 'MQ CR72' dispersion model R2eff calculating functions.

The numpy.arccosh() function can handle all input values when complex, therefore the checks for the
real part being above 1 are not necessary.

Fix for the 'MQ CR72' dispersion model target function.

The correct R20 values are now extracted from the parameter vector.

Removed a latent bug in the 'MMQ 2-site' dispersion model.

This was not being seen but might have caused problems in the future.

Fixes for the 'MQ CR72' dispersion model target function.

The relax_disp.plot_disp_curves user function can now handle values of NaN.

These are simply replaced by 0.0 to allow Grace to open the file.

Another bug fix for the 'MQ CR72' dispersion model.

The nu_CPMG value rather than the relaxation time was being used to calculate the R2eff values as
the division by 'n' was missing.

Fix for the 'MQ CR72' model for MQ-type data.

The check to prevent acos of a number less than 1 has been changed to switch the sign rather than to
set the back calculated R2eff to 1e99.

Converted the 'MQ CR72' dispersion model to handle MMQ data.

This model can now handle proton-heteronuclear SQ, ZQ, DQ, and MQ CPMG-type data. Some debugging
might still be required.