The Weingarten map is block-diagonal for a product space.

[[Imported from SVN: r9517]]

[[Imported from SVN: r9422]]

[[Imported from SVN: r9415]]

Because it may contain a projection onto the manifold, which
is part of the energy evaluation if we view the energy as
being defined on all of R^n (as ADOL-C does).

[[Imported from SVN: r9414]]

Not actually working yet, though.

[[Imported from SVN: r9412]]

[[Imported from SVN: r9395]]