Added this.  

I ran into some trouble with the (new) test_ChromaticAutoConvolve() unit test here, though.  I had thought that I could just reuse here the prof0 that I generated earlier to setup the output image.  This gave me a half-pixel offset from what I expected though, so I remade prof0.  Something regarding use_true_center I expect.

        # setup output image (semi-arbitrarily using the bandpass effective wavelength)
        prof0 = self.evaluateAtWavelength(bandpass.effective_wavelength)
        prof0 = prof0._fix_center(image, scale, offset, use_true_center, reverse=False)
        image = prof0._draw_setup_image(image, scale, wmult, add_to_image)

        if self.separable:
            # *why* do I have to do this?  Maybe there's another setting I should be altering
            # instead of redoing this profile?
            prof0 = self.evaluateAtWavelength(bandpass.effective_wavelength)