New template-less pure virtual API

TODO: Implement this new API.

Tobias favours it. Don't know how it goes with optimized kernels. SMall patch for the piucture from Tobias:

  /* NEW: */
   kernels::aderdg::generic::c::spaceTimePredictorLinear(BasisSolverAPI&  solver, other parameters ... );

In textual form Sketch.h