Better handling of SExtractor masks

[MorganSchmitz]

As very rightly pointed out by @jerome-bonnin, passing on binary masks to avoid SExtractor masks is not sufficient and the actual values in the star stamps should also be replaced to something more reasonable than the SExtractor default

Add a check at initialization that does this, with an option defaulting to False to turn it off (if you really want pixels at 10^423098 around for whatever reason)