Cosserat-Continuum-Nonplanar

@osander: Can you have a look here?

This MR cleans up the usage of MIXED_SPACE in cosserat-continuum.

Now all combinations of dim = dimworld or dim != dimworld and MIXED_SPACE = 0 or MIXED_SPACE = 1 at least compile.

Also, this MR points out the one combination that still can't be solved: Problems with dim != dimworld do not work for MIXED_SPACE = 1!

As soon as I need this for locking tests I will add this; I will have to change Nonplanarcosseratshellenergy so it can be assembled with the GFEMixedAssembler.

src/CMakeLists.txt

 set(programs compute-disc-error
-             cosserat-continuum
              gradient-flow
              harmonicmaps
              rod3d)
 #            rodobstacle)
 
+if (${DUNE_FUNCTIONS_VERSION} VERSION_GREATER_EQUAL 2.7)
+  set(programs cosserat-continuum ${programs})
+endif()
 if (dune-parmg_FOUND AND dune-curvedgeometry_FOUND AND ${DUNE_ELASTICITY_VERSION} VERSION_GREATER_EQUAL 2.8)
 	set(programs film-on-substrate ${programs})
 endif()