GenericGeometry backport.

The current fix is to throw Dune::NotImplemented, though

NOTE: 'make test' was replaced by 'make build_tests && make test'

This reverts commit af3fde69.

are stored using std::unique_ptr.

[feature] Allow construction of simplices using different simplex element types (only for bisection refinement).

bisection refinement.

the test refines a 3d ball with a projection
and calculates the error to the real ball
this should reduce over refinement

With this patch, Entity::father, Entity::subEntity,
IntersectionIteratorWrapper::inside and IntersectionIteratorWrapper::outside
return entities instead of entity pointers.

Warning: This will definitely break compatibility with the 2.3 release.

the problem was that the search for the periodic neighbour deletes the periodic
boundary faces from the boundary and the elements get oriented between insertion
and this. So it does not find the elements. Now the search is done after the recreation of
the boundaryIds with respect to the new element orientation

GCC with -Wall will warn about the latter.