Provide functions for C++11 range-based for loops. Document C++11 interaction

This is a pull request to address at least in parts issue 239:
  https://code.google.com/p/dealii/issues/detail?id=239
It creates new functions in Triangulation, DoFHandler and hp::DoFHandler that return objects that can be used in range-based for loops. The IteratorRange class supports this.

The pull request also introduced a new documentation module C++11 that documents how we interact with C++11 and what features we provide in support of this.
I made it a module so I can add things to it. For example, I added namespace std_cxx1x to it and was planning to add the new functions in Triangulation and DoFHandler to it. We may have other things in the future that naturally would make for good additions to this group.