relax SVN archive

Create the interface for the pcs.centre() user function.

Added the frq and temperature modules to the __all__ list.

Fixes for the frq.set() user function.

Activated the frq.set() user function.

Wrote the spectrometer frequency setting function generic_fns.frq.set().

Added the frq and temperature modules to the __all__ list.

Added the user function interface for setting the spectrometer frequency of an experiment.

Made the experimental id string compulsory.

Completed the generic_fns.temperature.set() function.

Allowed the temperature to be entered as a integer as well as a float.