make LoopKernel.__init__ leaner (#293)
* move get_outer_params out of LoopKernel.__init__ * make LoopKernel.__init__ leaner - move domain checks out of it - trigger domain checks in copy iff it was passed as an input * LoopKernel.get_copy_kwargs() a better place to update 'kwargs' * get_copy_kwargs: handle iname_to_tags deprecation better