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/cosserat-continuum.cc

@@ -63,7 +63,7 @@
 #endif
 
 #ifndef WORLD_DIM
-#  define WORLD_DIM 3
+#  define WORLD_DIM 2
 #endif
 const int dimworld = WORLD_DIM;