Added recursion protection to cmake recusion step

Also added swig lookup test
Changing filenames
Simplifying boost lookup (Issue #55)
Adding tbb lookup (Issue #56)
Unsets TBB variable if partially found

Makes sure that TBB is found fully or not at all. Otherwise could end up with debug library from one
version and release from another.
remove debug message
Redesigned recursive cmake step

Now checks whether a required package is found after installation
Adding dune external installer (Issue #58)

* Downloads and installs dune-common dune-geometry dune-grid dune-local functions, each as a
  separate external package. Configures, builds, and installs using the new "experimental" cmake
  build system.
* Copies dune-foamgrid from contrib in source. Installs it as an external project by first
  "patching" it with a small cmake script that detects *.hh files.
* Adds an external project that creates a dummy duneproject module. Configure and builds it. Now we
  have an official config.h file from the dune project. installs it as dune-config.h
* Have yet to look at other patches from the series.