fix script/gen_gallery.py for new time stepping
fix script/gen_gallery.py for new time stepping

BubuLK/sfepy,RexFuzzle/sfepy,rc/sfepy,vlukes/sfepy,vlukes/sfepy,BubuLK/sfepy,RexFuzzle/sfepy,sfepy/sfepy,rc/sfepy,sfepy/sfepy,sfepy/sfepy,RexFuzzle/sfepy,vlukes/sfepy,RexFuzzle/sfepy,lokik/sfepy,rc/sfepy,lokik/sfepy,lokik/sfepy,lokik/sfepy,BubuLK/sfepy