In this file we define lipschitz consisting all the elements in (clifford_algebra)ˣ closed
under conjugation and construct pin_group based on lipschitz and unitary, and we construct
spin_group based on pin_group and clifford_algebra.even. Also, we show pin_group and
spin_group form a group where the inverse is star.
lipschitz: the Lipschitz group with a quadratic form.pin_group: the Pin group with a quadratic form.spin_group: the Spin group with a quadratic form.