Erasing of Peano grid vertices

Currently, I remove only my data from the heap when I erase a cell. The Peano grid structure still persists.

I tried a variety of tricks to remove the grid structure on the fly during the mesh refinement but always run into problems:

• Inconsistent adjacency indices
• Spurious erases of neighbours
• Data races with TBB
• ...

I think now it does make more sense to erase Peano vertices after the mesh refinement. Here the refined grid is fixed. Refinement does not interfere with erasing. I think of either:

• Erase Peano vertices on the fly during the time stepping iterations however I do not know the overhead and impact on the parallelisation.
• Run a few iterations of a dedicated mesh erasing adapter after the refinement.