Ellipsoid VTK output

See merge request walberla/walberla!85

External apllications which did not set the C++ standard to 14 in their CMakeLists.txt failed to build. This change allows them to build without further user actions.

Require C++14 and CMake 3.1

See merge request !79

- Avoid that defining points are aligned on a Plane
- Improve numerical stability of cross product

- cellIntervalToSlice more flexible

fix MPIEXEC_PREFLAG

See merge request walberla/walberla!80

Also remove some unneeded boost includes

Resolve "body filter to exclude bodies from PeVTKMeshWriter"

Closes #47

See merge request walberla/walberla!77

Resolve "Rename setMass function"

Closes #46

See merge request walberla/walberla!75

Dynamic refinement for pe module

See merge request walberla/walberla!52