Add isApprox in Geometry module's classes.

Complete unit tests wrt previous commits.

Eigen/src/Geometry/Translation.h

@@ -145,6 +145,13 @@ public:
   inline explicit Translation(const Translation<OtherScalarType,Dim>& other)
   { m_coeffs = other.vector().template cast<OtherScalarType>(); }
 
+  /** \returns \c true if \c *this is approximately equal to \a other, within the precision
+    * determined by \a prec.
+    *
+    * \sa MatrixBase::isApprox() */
+  bool isApprox(const Translation& other, typename NumTraits<Scalar>::Real prec = precision<Scalar>()) const
+  { return m_coeffs.isApprox(other.m_coeffs, prec); }
+
 };
 
 /** \addtogroup GeometryModule */