New wavelength_tolerance parameter

A common problem when processing multiple datasets with xia2 is when a small difference in the wavelength recorded in the image headers causes the sweeps to be grouped into more than one wavelength, when the desired outcome was for them to be processed as a single wavelength. Previously it was necessary to manually edit the .xinfo file to tell xia2 to process them as a single wavelength. Now we have added a new parameter wavelength_tolerance (default=0.0002 Å) which you can use to control whether or not different wavelengths get grouped together as a single wavelength.

Example usage:

xia2 -3dii wavelength_tolerance=0.001 /path/to/images/