[Dune] Interface change in dune-disc/operators

[Oliver Sander]

Dear users of dune-disc!
There has been an interface change in the assembler framework of dune-disc.
Here is the commit message for those who don't usually read commit messages:

'Some cleanup of the assembler framework.  The deprecated class 
IntersectionGetter
is not used anymore.  Instead, the relevant information is taken from 
the GridView.
As a result, the method LocalStiffness::assemble() is not a member template
anymore.  Consequently, there is no more need for the Barton-Nackman 
trick in
LocalStiffness, and it uses textbook dynamic polymorphism now.

I also introduced a new class LinearLocalStiffness which inherits from 
LocalStiffness.
This will eventually enable the global assembler to distinguish between 
linear
and nonlinear problems using RTTI.

Nota bene: this is an interface change.  You'll have to change the following
things in your code:
- If you use descendants of LocalStiffness: the first template parameter is
  a GridView now, not a Grid
- If you maintain descendants of LocalStiffness:
  - if they are linear, inherit from LinearLocalStiffness now
  - the methods assemble() and assembleBoundaryConditions() are no member
    templates anymore
  - The first template parameter of LocalStiffness (Imp) has been removed.

Enjoy!'

--
Oliver


-- 
************************************************************************
* Oliver Sander                ** email: sander at mi.fu-berlin.de        *
* Freie Universität Berlin     ** phone: + 49 (30) 838 75217           *
* Institut für Mathematik      ** URL  : page.mi.fu-berlin.de/~sander  *
* Arnimallee 6                 ** -------------------------------------*
* 14195 Berlin, Germany        ** Member of MATHEON (www.matheon.de)   *
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