* systematic encoding of fetype enum (also added P2DFE)
* global to local dof-management and assignments for P2DFE
* accumulator-concept also for loops over faces (e.g. for error estimators or DG jump terms)
* vtk Output for P2DFE-Function (but inactive here)
* introducing "Discontinuous" property for Levelset-section in json-files (no impact yet)
* vtk output with P2DG-flag now (flag is active)
* Accumulator for DG matrices (not used yet)
* LevelsetP2CL becomes BaseClass for LevelsetP2ContCL and LevelsetP2DiscontCL
* LevelsetP2CL-BaseClass::Create replaces constructor in many executables
* access to Lset.PhiC at several places (instead of access to Lset.Phi) ensures that a continuous quantity is used (either cg-levelset or clement-interpolated dg-levelset)
* FaceAccumulators and Setup for DG-Levelset-Systems (Levelset-system might have a rhs stemming from weakly coupled boundary conditions in DG => Changes in Coupling)
* Clement-interpolated continuous Phi needs to be updated every once in a while ( => changes in coupling)
* minor (comments)
* buildsystem fix for f_gamma-test (dependencies on shared libs added)
* Levelset DG is off by default
merge from the master branch, mainly the DG method for levelset
* fix the bug also in SpecialBndHandler for twophase case