remove generic geometry subdirectory

On the last developer meeting, we agree on the following things:

• The genericgeometry subdirectory should vanish in the next DUNE release.
• All content of the namespace GenericGeometry is considered an implemenation detail.

This merge implements these decisions. All functionality that is sitll required is migrated into the appropriate headers in dune/geometry and put into the namespace Impl.

Note: There is no transition phase for the content of the genericgeometry subdirectory.

Mentioned in issue #4 (closed)

Added 2 commits:

• eeb233f1 - remove unused helper Topology
• 4e554159 - use a variadic template in IfTopology

Added 1 commit:

• 1cf9e000 - mark helper function 'inline static' and 'noexcept'

Added 4 commits:

• 7e45d0d4 - remove unused SubTopologyMapper
• a7a1780e - remove unused SubTopologySize, GenericSubTopologyNumbering, and SubTopologyNumbering
• a103bfb5 - further simplify IfTopology
• d48a651e - remove now unused GenericGeometry::SubTopology

Added 1 commit:

• d91a69dc - remove unused GenericGeometry::Size

Added 1 commit:

• 9ccc5ec7 - migrate computation of subtopologies to referenceelement.hh

Added 1 commit:

• 2a0f48db - incorporate genericgeometry/topologytypes.hh into type.hh

Unmarked this merge request as a Work In Progress

Please merge this MR or I am going to do so. We should get it to master then it gets tests on a broader basis. That should help to gain confidence for a inclusion to Dune 2.5.

Status changed to merged

Mentioned in commit 76b1d4bf

Mentioned in merge request dune-localfunctions!26 (merged)

Mentioned in commit 51779cd5

Mentioned in merge request !38 (merged)

Mentioned in commit 2ed17720