[Dune] Reference topologies

[Oliver Sander]

Hi guys!
I just checked in a bare-bones reference topologies mechanism.
It lets you query the vertices of subfaces of elements, and it
answers fast.
As I mentioned before I am not very happy with the design of
this utensil, and I consider my implementation a preliminary
one.  We may want to trade a bit of speed for some more
elegance.  We may also want to fuse the whole thing with the
existing ReferenceTopology and ReferenceElement stuff.
I strongly suggest we put the whole thing on the agenda for
the next group discussion.

--
Oliver

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* Oliver Sander                **                                      *
* Freie Universität Berlin     ** email: sander at math.fu-berlin.de      *
* Institut für Mathematik II   ** phone: + 49 (30) 838 75217           *
* Arnimallee 2-6               ** fax  : + 49 (30) 838 54977           *
* 14195 Berlin, Germany        ** URL  : www.math.fu-berlin.de/~sander *
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