add cast<newtype>() function to casts the scalars to another type.

src/Core/Conjugate.h

@@ -42,7 +42,8 @@ template<typename MatrixType> class Conjugate
     Conjugate(const Conjugate& other)
       : m_matrix(other.m_matrix) {}
     
-    EI_INHERIT_ASSIGNMENT_OPERATORS(Conjugate)
+   // assignments are illegal but we still want to intercept them and get clean compile errors
+   EI_INHERIT_ASSIGNMENT_OPERATORS(Conjugate)
     
   private:
     const Conjugate& _ref() const { return *this; }