relax SVN archive

Made the user function spectrum.sn_ratio smaller.

Added float around values in signal_noise_ratio() function.

For the specific analysis of "noe", "relax_disp", and "relax_fit", initialised the sn_ratio parameter structure.

Added the common API Parameter structure 'sn_ratio' in parameter_object.

Added systemtest Spectrum.test_grace_sn_ratio to help implement plotting the signaÃl to noise ratio per residue.

Added systemtest Spectrum.test_grace_int, to test plotting the intensity per residue.

This is to prepare for a grace plotting of the signaÃl to noise level per residue.

Also added additional tests for signal to noise ratio calculation in the systemtest Spectrum.test_signal_noise_ratio.

Added the pipe_control.spectrum.signal_noise_ratio() backend function, for calculation of the signal to noise ratio per spin.

Added user function spectrum.sn_ratio to calculate the signal to noise ration for all spins.

Added the systemtest Spectrum to the init file, so the systemtest can be executed.

Initialised first test in systemtest Spectrum.

This is simply loading some intensity data, and checks data.

The systemtest test Spectrum.test_signal_noise_ratio will be expanded to test the calculation of the signal to noise ratio.