This avoids 'implicit narrowing' errors/warnings.

Using LocalIndexSet objects was mandatory with dune-functions-2.5
and earlier.  However, we only support 2.6 and later anyway,
so let's get rid of the backward-compatibility code.

Throw out the AmiraMesh support instead.  I have not seen
anybody using Amira for years.

But keep compatibility with dune-grid 2.6 as well.

It's the same code, but the old name is deprecated.

I think they used to have one, back in the day of the EntityIterator
class.

Transformed the surrounding loop to range-based-for syntax
while I am there.

Rationale
a) Code is much simpler without it
b) Code compiles faster without it
c) P3 functions are now downsampled to P2 functions, rather than to P1 functions.
   Hence there is less loss of information now.

Simply ask the first local finite element of the dune-functions basis for the order.

[[Imported from SVN: r10087]]

Use MPIHelper instead.

[[Imported from SVN: r9908]]

[[Imported from SVN: r9906]]

[[Imported from SVN: r9895]]

[[Imported from SVN: r9894]]

It is not used anymore.  On the other hand, I want to get rid of 
GeometryGrid in the CosseratVTKWriter.  Now with the new VTKFile
at hand there is a chance.

[[Imported from SVN: r9893]]

[[Imported from SVN: r9892]]

[[Imported from SVN: r9883]]

ParaView doesn't support P3 elements.  Therefore, the data is
downsampled onto a p2 space.

[[Imported from SVN: r9863]]

[[Imported from SVN: r9859]]

'Mixed' means that there are two different spaces used for the
deformation and the microrotations.

This implementation currently only does second order, and it
only writes the deformation, not the microrotations.

[[Imported from SVN: r9848]]

[[Imported from SVN: r9777]]

Otherwise, all processes will write into the same file --> not a good idea.

[[Imported from SVN: r9776]]

Currently only for quadrilaterals.  I'll implement triangles as soon
as I need them.

Unfortunately, VTK appears to only support 8-node quadrilaterals
(without an element dof).  So the element dofs get ignored currently.

[[Imported from SVN: r9756]]

With this patch we start to differentiate according the the function
space bases of the input data.  We write P1 data as is, and downsample
P2 and P3 data onto a P1 space.

[[Imported from SVN: r9755]]

[[Imported from SVN: r9754]]

This makes visualizing wrinkles much easier.

[[Imported from SVN: r9753]]

[[Imported from SVN: r9666]]

That way, they can at least be looked at.  You won't see the intra-element
details, but frequently they are not even all this important.  Proper
subsampling of higher-order functions is more difficult and has to wait
for another day.

[[Imported from SVN: r9665]]

This will be generalized to take any Lagrange basis, to allow some form
of visualization for higher-order functions.

[[Imported from SVN: r9662]]

[[Imported from SVN: r9614]]

[[Imported from SVN: r8385]]

[[Imported from SVN: r8384]]