check_gpuecm.sage add smallestGroupOrder

This allows for

$ sage --preparse check_gpuecm.sage
$ mv -f check_gpuecm.sage.py check_gpuecm.py
$ sage --python -c "import check_gpuecm; check_gpuecm.smallestGroupOrder(13526662966442476828963, 2, 10000, 1000)"
and possibly
$ python -c "import check_gpuecm; check_gpuecm.smallestGroupOrder(594538100848945223169882301931953, 3, 10, 1000)"

Which can help find B1/B2 limits for tests where prime will be found.