Ability to select scattering range by size

[josephhardinee]

The 2DVD instruments, as well as others, have diameter bins that get fairly large. This can cause issues for the underlying scattering code. We need to implement a feature that allows a max effective scattering parameter to be introduced to the object. Something like

dsd.set_scattering_limits(0, 8)

. We do need to discuss whether this should affect the dsd parameterization code as well or be limited to just the scattering. @nguy, your thoughts?

[nguy]

My first instinct is to limit to the scattering code. BUT that said, this could be carried as an attribute in the readers and be used to mask (or limit the data) introduced into the scattering code.