Removed caused of NPE
Added fit sub-package back to default import
Removed fixed tilt fit functions, reverted global threshold to previous
value, fixed finding ellipses that are smaller than previously fitted,
added and used fixed wavelength function for circular case
Added positive min and max methods which are handy for calculating range
of logged values
Added support for filtering infinities in compound dataset stats
Added support for filtering infinities for global stats in compound
datasets and some unit tests for positive max and min