relax SVN archive

The new parameter keys are based on the experiment type and the spectrometer frequency. These keys
are supported by the generate_r20_key() and decompose_r20_key() pair of functions in the
specific_analyses.relax_disp.disp_data module. This enables support for different R20 parameters
for each experiment type - a key piece of infrastructure for the MMQ models.

The relax_disp.select_model user function backend was modified so the parameter list only contains
one instance for each of the 'r2', 'r2a', or 'r2b' strings.

The specific_analyses.relax_disp.parameters.loop_parameters() function was modified so that the R20
key rather than frequency index is returned for the R20 parameters. Many other code changes were
required.