[Dune] change to inheritance of vtksequencewriter

[Andreas Dedner]

Hi.
Was this change discussed?
It breaks code. Up until now you could write a method
addMyData(VtkWriter<..> &)
which could then either take a sequence writer or a simple vtk writer.
This code
is broken now (used e.g. in the examples in dune-alugrid).
So this change is not backward compatible and at the moment I don't even
see a workaround
except to write two addMyData methods.
Did I miss the discussion?
Andreas

commit 03898df8b04538b577426bdf5e93740cb0fdcf62
Author: Oliver Sander <sander at igpm.rwth-aachen.de>
Date:   Fri Sep 19 22:56:14 2014 +0200

    Implement VTKSequenceWriterBase without the Curiously Recurring
Template Pattern
    
    ... and without multiple inheritance.  It is simpler that way, and
not less
    efficient.