known bugs:

* evaluateFactor() in integralterm.hh is called with the *local* position
  of a given quadrature point, this should be first transformed into
  global coordinates. (Already fixed but not tested for interior implementation,
  has to be fixed for face implementation)
* PQkTransportBasis cannot be used as a test space at the moment.
  There are compile-time errors that are probably caused by using
  ChooseQuadrature without specifying the transport direction β.
* Adjust quadrature order for non-constant function (rhs term) in
  getvolumeterm_impl.hh and in linearintegralterm.hh

technical debt that needs to be paid off sooner or later:

* Replace boost::fusion with dune/common/tupleutility.hh or use
  dune-typetree instead of std::tuple.
* Beginning with version 1.58 boost::fusion has better support for std::tuple,
  thus we can maybe get rid of those boost::fusion::vectors.
