In particular, MonotoneMultiGridStep use shared_ptr much more
frequently now.  Also, various of its data members are now
protected, and getters/setters have to be used.

It used to be in dune-functions originally, but got moved to
dune-common eventually.  This patch updates the code to reflect
that move.

I think they used to have one, back in the day of the EntityIterator
class.

Transformed the surrounding loop to range-based-for syntax
while I am there.

The one in the Arithmetic namespace does not exist anymore.

And some other Dune 2.4 stuff.

It has been removed from dune-functions in the last release
(at least).

Previously, the actual projection happened by calling the constructor
of one of the classes that implements points on a manifold.  This patch
introduces an new method projectOnto, which makes the projection more
explicit.

- use more shared_ptr
- New MCMGMapper interface from dune-grid 2.6
- basis.indexSet() has been removed from dune-functions

Makes it faster, but only by 1 or 2 percent.

The new value is what you need for linear target spaces.
I am not convinced that this is sufficient, but it matches
what we do for simplices.

The whole quadrature business will need some theoretical
investigations eventually.

Only cmake is supported from now on.

A lot of raw pointers have been replaced by std::shared_ptr.

A lot of data members are inaccessible now, and getters have
to be used.

A small patch is still needed for dune-solvers: The iterationStep_
member is still needed to be public, because the new getter only
grants access to the object, not the pointer to it.

When switching to the double covered quaternion pair, the
corresponding distance was not computed correctly

Make them a parameter instead.  This allows to switch more easily between
geodesic finite elements and projected finite elements.

Make them a parameter instead.  This allows to switch more easily between
geodesic finite elements and projected finite elements.

It still tested for the dune-fufem wrapper of a first-order basis, while nowadays
the RiemannianTRSolver class is instantiated with dune-functions bases.