Big change in DiagonalMatrix and Geometry/Scaling:

* previous DiagonalMatrix expression is now DiagonalMatrixWrapper
* DiagonalMatrix class is now for storage
* add the DiagonalMatrixBase class to factorize code of the
  two previous classes
* remove Scaling class (it is now a global function)
* add UniformScaling helper class
  (don't use it directly, use the Scaling function)
* add the Scaling global function to simplify the creation
  of scaling objects
There is still a lot to do, in particular about DiagonalProduct for which
the goal is to get rid of the "if()" in the coeff() function. At least
it is not worse than before ! Also need to uptade the tutorial and add more doc.

Eigen/src/Geometry/Quaternion.h

@@ -193,8 +193,7 @@ public:
 
   Quaternion slerp(Scalar t, const Quaternion& other) const;
 
-  template<typename Derived>
-  Vector3 operator* (const MatrixBase<Derived>& vec) const;
+  Vector3 operator* (const Vector3& vec) const;
 
   /** \returns \c *this with scalar type casted to \a NewScalarType
     *
@@ -256,17 +255,15 @@ inline Quaternion<Scalar>& Quaternion<Scalar>::operator*= (const Quaternion& oth
   *   - Via a Matrix3: 24 + 15n
   */
 template <typename Scalar>
-template<typename Derived>
 inline typename Quaternion<Scalar>::Vector3
-Quaternion<Scalar>::operator* (const MatrixBase<Derived>& v) const
+Quaternion<Scalar>::operator* (const Vector3& v) const
 {
     // Note that this algorithm comes from the optimization by hand
     // of the conversion to a Matrix followed by a Matrix/Vector product.
     // It appears to be much faster than the common algorithm found
     // in the litterature (30 versus 39 flops). It also requires two
     // Vector3 as temporaries.
-    Vector3 uv;
-    uv = 2 * this->vec().cross(v);
+    Vector3 uv = Scalar(2) * this->vec().cross(v);
     return v + this->w() * uv + this->vec().cross(uv);
 }