[Dune] Maximal level difference

[Carsten Gräser]

Dear dune,
in dune-subgrid we implemented a simple method to automatically
add refinement marks and remove coarsening marks such that
the level of neighboring elements differs at most by a user
defined number. (ALUGrid e.g. does this internally).

As someone asked for this functionality in UGGrid I extracted
this using the grid interface only. This might also be helpfull
for other third party grid implementations.

Are there any objections to add this to dune/grid/utility?

Regards,
Carsten

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Carsten Gräser           | phone: +49-30 / 838-75349
Freie Universität Berlin | fax  : +49-30 / 838-54977
Institut für Mathematik  | email: graeser at math.fu-berlin.de
Arnimallee 6             |
14195 Berlin, Germany    | URL  : http://page.mi.fu-berlin.de/graeser
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