Convert PsfexPsfDeterminerTask to use new AlgorithmError exceptions

Now that we have working examples of the new AlgorithmError in MeasureApCorrTask and AstrometryTask, convert PsfexPsfDeterminerTask to raise this error for algorithmic failures (the exceptions related to number of sources are good candidates, but I think the two about loading from the psfex context probably aren’t). This will let e.g. CalibrateImage write partial outputs for “known” psf measurement failure modes.