Implement element dof iterator class. May be used to iterate over all dofs of one element independent of dimension and degree of basis functions.

No commit message

Added files for InteriorBoundary, a class that defines a boundary within the domain. This is used for domain decomposition parallelization.

* First support for independent meshes for different components

* Traverse:recursive uses ElInfoStack and is much faster :)

* Added DuneSolver

- Umfpack breaks, if the final residual is larger than the given tolerance