- performance improvement: added AVX support for TimeStepDFSPH, DragForce_Gissler2017, Viscosity_Standard, Viscosity_Weiler2018, MicropolarModel_Bender2017
- added AVX support for 2D simulations
- added VTk export of rigid bodies
- added parameter to control min CFL step size
- cleaned up classes of graphical user interface
- exchanged Static/DynamicBoundarySimulator by SPHSimulator which can handle dynamic and static scenes
- added regular surface sampling
- updated to Eigen 3.3.7
- bugfixes