Changes for the spectrum.read_intensities user function dim argument.

The default is now w1, the indirect dimension in a 2D experiment.  The description has also been
fixed.
Fixes for all of the peak intensity reading functions - the w1 and w2 dimensions were swapped.
Updates to the sample scripts for the spectrum.read_intensities user function argument changes.
Updates to the user manual for the spectrum.read_intensities user function argument changes.