relax SVN archive

Copied the script for the fast-exchange regime to the slow-exchange regime.

Added an unresolved file to meet the script requirements.

Changed the format of the CPMG frequency and corrected the names of some input files.

Added 'Sparky' formatted files to the system-test so the files can be input and development of the
branch continued.

Added a relaxation dispersion dataset in the system-test.

This was kindly provided by Dr Flemming Hansen (flemming AT pound DOT med DOT utoronto DOT ca) and
was previously published in: Hansen, Vallurupalli & Kay, 2008, JPhysChemB, 112: 5898-5904.

The original format was different and was modified to better suit the way relax handles datasets.

Finally, the information contained here were written in a 'readme' file placed in the same
directory as the dataset itself to allow referencing and acknowledgments.

Changed the default cpmg_frq value in cpmg_frq() from 0 to None.

Corrected a few dosctrings.

Corrected some print outs...

Introduced relaxation dispersion parameters in the function return_data_name().

Introduced CPMG parameters into the function return_grace_string() and corrected formatting issues.