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]]

The CosseratStrain object is a 3x3 matrix, where the last column
is (0,0,1)^T.  This special structure allows to use specially tuned
matrix methods (e.g., the determinant), which I intent to do in the
future.

[[Imported from SVN: r9752]]

[[Imported from SVN: r9751]]

[[Imported from SVN: r9749]]

And use it in one place in VectorCommunicator

[[Imported from SVN: r9748]]

[[Imported from SVN: r9747]]

[[Imported from SVN: r9746]]

[[Imported from SVN: r9744]]

The Dirichlet nodes are handled directly via the ignoreNodes_ field.
I don't know how the matrix modification code ever got in here.

Removing the code doesn't seem to make any difference.  I find that
a bit surprising: I would expect multigrid and IPOpt to work better
if the matrix is truly symmetric.

[[Imported from SVN: r9742]]

Much easier to use than the previous API.

[[Imported from SVN: r9735]]

[[Imported from SVN: r9734]]

[[Imported from SVN: r9733]]

[[Imported from SVN: r9732]]

[[Imported from SVN: r9731]]

Those do many-to-one communication with a single method call.
Previously, two subsequent calls were needed.  There is no reason
why the interface has to consist of two calls.  A single one is
much easier to use.

[[Imported from SVN: r9730]]

[[Imported from SVN: r9729]]

After much back and forth: this is the correct way.  This size cannot
be taken from the transfer operators, because these operators exist
only if there is more than one level.

[[Imported from SVN: r9728]]

[[Imported from SVN: r9727]]

[[Imported from SVN: r9726]]

That works for fe spaces of all orders.

[[Imported from SVN: r9725]]

[[Imported from SVN: r9724]]

[[Imported from SVN: r9723]]

[[Imported from SVN: r9721]]

Christian Engwer told me a trick how to get the mpiHelper instance without
known argc and argv.

[[Imported from SVN: r9720]]

That way we can handle multigrid transfer matrices as well.

[[Imported from SVN: r9719]]

The globalindex.hh and uniqueentitypartition.hh is from Benedikt Oswald.
The rest is from Benjamin Bykowski, with a few fixes from me.

The globalindex stuff should go into dune-grid eventually, but it needs
some polishing first.

[[Imported from SVN: r9718]]

[[Imported from SVN: r9710]]

[[Imported from SVN: r9709]]

[[Imported from SVN: r9708]]

This does what we want both on one and on many processors.

[[Imported from SVN: r9707]]

This has two advantages:
- The two matrices use different number types (adouble vs. double),
  but the generic multiplication in dune/istl/matrix.hh doesn't support
  that.  Hence before this change I had to patch dune-istl.
- It avoids one extra copying operation

[[Imported from SVN: r9703]]

[[Imported from SVN: r9702]]

[[Imported from SVN: r9701]]

[[Imported from SVN: r9693]]

[[Imported from SVN: r9692]]

With the better initial iterate introduced in the previous patch,
this lower number seems to be sufficient.

[[Imported from SVN: r9684]]

The new initial iterate is constructed by interpolating the values in Euclidean
space, and projecting back onto TargetSpace.  This has two advantages:
1) It's a better initial iterate, so we should converge faster than starting
   from coefficients_[0]
2) It makes it easier for ADOL-C to pick up correct second derivatives.
   Hence we are able to reduce the minimum number of iterations of the
   target space tr solver.

[[Imported from SVN: r9683]]