from a Pk-basis to a P1-basis.

Doesn't work beyond P2 yet, I'll fix that in a second.

Should eventually go into dune-solvers.

[[Imported from SVN: r8218]]

[[Imported from SVN: r7966]]

[[Imported from SVN: r7955]]

[[Imported from SVN: r7924]]

[[Imported from SVN: r7921]]

[[Imported from SVN: r7899]]

And use it to implement the Rotation<3> class.  This makes the
Rotation implementation easier to understand.  Previously we
have used a FieldVector<3> when a skew matrix was meant.
This leads to confusion now that we also use quaternions as
tangent vectors of SO(3).  In local coordinates, these also
have 3 entries.  Adding the new skew matrix class makes it
clearer what kind of mathematical object is meant.

[[Imported from SVN: r7897]]

[[Imported from SVN: r7547]]

[[Imported from SVN: r6743]]

[[Imported from SVN: r6722]]

[[Imported from SVN: r6721]]

This class should centralize some of the logistics needed for the knee
models and similar stuff.  Eventually, domain decomposition solvers should
be able to work on this data structure.  That is still a way off, though.

[[Imported from SVN: r6716]]

[[Imported from SVN: r6715]]

[[Imported from SVN: r6714]]

[[Imported from SVN: r6046]]

[[Imported from SVN: r5936]]

[[Imported from SVN: r5931]]

globally refine a grid and transfer a given function to the next level.  Works for all TargetSpaces and replace rodRefine, which did the same only for RigidBodyMotions

[[Imported from SVN: r5771]]

[[Imported from SVN: r5636]]

[[Imported from SVN: r5560]]

[[Imported from SVN: r5323]]