DM-12103: Investigate centering for vignetted pupils

[jmeyers314]

Adds _centerPupil function and **kwargs to getPupilFactory to
optionally recenter the illuminated portion of a pupil within
a pupil array, similar to what is done in Zemax.

[mfisherlevine]

Personally I'd use slightly different indentation in that method for clarity, but I can see what you've done is flake8 compliant, so if you feel strongly that this way is clearer/better you can leave as is. My preference:

    def _centerPupil(self, pupil):
        """Center the illuminated portion of the pupil in array.

        @param[in,out] pupil  Pupil to modify in place
        """
        def center(arr, axis):
            smash = np.sum(arr, axis=axis)
            w = np.where(smash)[0]
            return int(0.5*(np.min(w)+np.max(w)))
        ycenter = center(pupil.illuminated, 0)
        xcenter = center(pupil.illuminated, 1)
        ytarget = pupil.illuminated.shape[0]//2
        xtarget = pupil.illuminated.shape[1]//2
        pupil.illuminated = np.roll(np.roll(pupil.illuminated,
                                            xtarget-xcenter,
                                            axis=0),
                                    ytarget-ycenter,
                                    axis=1)

[mfisherlevine]

Looks good. Just change this commit message to have the same first line as the other one (first word in the imperative and all that), and move this one to be after a line break to make the bulk of the message.

Other than that, and my OOB comment on the indentation about the in the _centerPupil() method I think you're good to go.