- introduce Part and Extract classes, splitting and extending the former

Triangular class
- full meta-unrolling in Part
- move inverseProduct() to MatrixBase
- compilation fix in ProductWIP: introduce a meta-selector to only do
  direct access on types that support it.
- phase out the old Product, remove the WIP_DIRTY stuff.
- misc renaming and fixes

Eigen/src/Core/Transpose.h

@@ -127,7 +127,7 @@ MatrixBase<Derived>::transpose() const
 template<typename Derived>
 inline const Transpose<
                Flagged<CwiseUnaryOp<ei_scalar_conjugate_op<typename ei_traits<Derived>::Scalar>, Derived >
-               , TemporaryBit, 0> >
+               , NestByValueBit, 0> >
 MatrixBase<Derived>::adjoint() const
 {
   return conjugate().temporary().transpose();