* vectorize dot product, copying code from sum.

* make the conj functor vectorizable: it is just identity in real case,
  and complex doesn't use the vectorized path anyway.
* fix bug in Block: a 3x1 block in a 4x4 matrix (all fixed-size)
  should not be vectorizable, since in fixed-size we are assuming
  the size to be a multiple of packet size. (Or would you prefer
  Vector3d to be flagged "packetaccess" even though no packet access
  is possible on vectors of that type?)
* rename:
  isOrtho for vectors ---> isOrthogonal
  isOrtho for matrices ---> isUnitary
* add normalize()
* reimplement normalized with quotient1 functor

test/geometry.cpp

@@ -86,7 +86,7 @@ template<typename Scalar> void geometry(void)
   m << v0.normalized(),
       (v0.cross(v1)).normalized(),
       (v0.cross(v1).cross(v0)).normalized();
-  VERIFY(m.isOrtho());
+  VERIFY(m.isUnitary());
 
   // AngleAxis
   VERIFY_IS_APPROX(AngleAxis(a,v1.normalized()).toRotationMatrix(),