Added the TSMFK01 model to the user_functions/relax_disp.py select_model user function frontend.

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>
Created the TSMFK01 model target function for 2-site very-slow exchange model, range of microsecond to second time scale.

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

The function is probably not correct, since there is some problems with using the end_index
to handle the unpacking of the parameters.

Signed-off-by: Edward d'Auvergne <edward@nmr-relax.com>
Added the TSMFK01 model equations to the relax library: lib/dispersion/tsmfk01.py

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>