Correct the stopping criterion in the Riemannian-TR-Solver, Riemannian-PN-Solver and MixedRiemannian-TR-Solver

Do not stop if the correction gets small because the trust region radius gets small or the regularization parameter gets large

They are getting removed now for good after the release of
dune-fufem 2.9.  The code that replaces them has been there
for quite a while, and therefore we can simply use it
without having to worry about compatibility with older
dune-fufem versions.

WHITESPACES: Wrap energy calculation and solve-call in the Mixed-Riemannian-TR solver in a try-catch statement

In case an error occurs while solving or calculating the energy, the program does not stop
but the error is handled in the Mixed-Riemannian-Trust-Region solver and the program continues
with a smaller trustregion-radius.

Apparently it is not used.

Up until dune-common 2.7, the Dune namespace contained shared_ptr:
First as an actual implementation, later simply as a namespace
import.  Dune-common post-2.7 has removed that import,
and users of shared_ptr really have to explicitly specify
the std:: namespace prefix.

This makes mixed-cosserat-continuum compile again.

The latter is deprecated as of dune-functions 2.6.

In particular, MonotoneMultiGridStep use shared_ptr much more
frequently now.  Also, various of its data members are now
protected, and getters/setters have to be used.

This leads to some simplification

This is an important step towards making the 'mixed' Cosserat code more like
the regular one.  The mid-term goal is to merge the two implementations, because
there is way too much code duplication here.

This makes 2nd-order orientation functions work again.

[[Imported from SVN: r10101]]

It appears that there may be very small energy increases due to
rounding errors.

[[Imported from SVN: r9867]]

[[Imported from SVN: r9860]]

[[Imported from SVN: r9858]]

[[Imported from SVN: r9857]]

[[Imported from SVN: r9856]]

'Mixed' means that the spaces for deformations and microrotations can
be chosen separately.

At this point there hasn't been a lot of testing yet.  In particular,
parallelizing the assembly is currently not supported.

[[Imported from SVN: r9852]]