relax SVN archive

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.

Corrected a typo found while coding in the 'relax_disp' branch.

A bit more changes to introduce parameters for CPMG relaxation dispersion.

Corrected a few formatting issues and still added parameters for the slow- and fast-exchange regime.

Formatting issues corrected were spotted by Ed in a post at:
https://mail.gna.org/public/relax-devel/2009-01/msg00045.html
(Message-id: <7f080ed10901091243k76e08449ld2d1a4d273b97f71@...>)

Corrected a few formatting issues and still added parameters for the slow- and fast-exchange regime.