Renamed ka parameter to kA, to be consistent with naming conventions.

Progress sr #3071: https://gna.org/support/index.php?3071 - Implementation of Tollinger/Kay dispersion model (2001)
Following the guide at: http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax

Troels E. Linnet provided this patch. Commit by: tlinnet _aaattt_ gmail_dot_com

Signed-off-by: Edward d'Auvergne <edward@nmr-relax.com>
Fix for r20 should be called r20a.

Progress sr #3071: https://gna.org/support/index.php?3071 - Implementation of Tollinger/Kay dispersion model (2001)
Following the guide at: http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax

Troels E. Linnet provided this patch. Commit by: tlinnet _aaattt_ gmail_dot_com

Signed-off-by: Edward d'Auvergne <edward@nmr-relax.com>
Fix for unpacking the parameters correctly.

Progress sr #3071: https://gna.org/support/index.php?3071 - Implementation of Tollinger/Kay dispersion model (2001)
Following the guide at: http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax

Troels E. Linnet provided this patch. Commit by: tlinnet _aaattt_ gmail_dot_com

Signed-off-by: Edward d'Auvergne <edward@nmr-relax.com>