Improvement of implementation of improveGrid-method

Improvements (?):

• tetrahedron mid points of bad elements are moved, too
• all grid levels are considered
• grid improvement is iterated until no vertices are to be moved

There has been no comment on this for 5 years. We should either merge or close this.

@oliver.sander_at_tu-dresden.de Can you have a look at this? I never touched/used improveGrid and it's also not tested.

For the record: This was proposed by Jakob Schneck, but the author was not preserved during the transfer of dune-fufem to gitlab.dune-project.org.

@oliver.sander Any opinion on this one? If we don't intend to merge this it should be closed.

I don't care either way. It looks okay, but I haven't used the code either for many many years.

I'll just merge this now, just to come to a decision. I don't know of anybody actually using this at the moment, which implies that such a merge cannot do much harm. :-)

merged

mentioned in commit 2b05b842