Improvements and addition of many links to the lib.dispersion.cr72 API documentation.

This is for the API documentation at:
http://www.nmr-relax.com/api/3.1/lib.dispersion.cr72-module.html.
Spacing fix for the lib.dispersion.cr72 module docstring.
Improvements and addition of many links to the lib.dispersion.dpl94 API documentation.

This is for the API documentation at:
http://www.nmr-relax.com/api/3.1/lib.dispersion.dpl94-module.html.