[Dune] Special quadrature rules.

[Christian Engwer]

Hello Robert,

> I suggest to move the Jacobi Quadrature rule dune-disc or a seperate
> module.

Jacobian Quadrature rules are part of this module, because they are
needed for constructing dim > 1 simplex rules.

> Therefore I think this
> quad rules should be moved to dune-disc.

If someone provides direct simplex rules for dim > 1 and higher order,
we can drop the Jacobian Rules; till then: No!

Cheers Christian