- fix for multiphase fluids

- added missing files

Require a specific sphinx version

- python fix

- linux build fix

- updated file_format.md

- performance improvement: added AVX support for TimeStepDFSPH, DragF…

…orce_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

- added the boundary handling method "Volume Maps: An Implicit Bounda…

…ry Representation for SPH"

- added the boundary handling method "Density Maps for Improved SPH Boundary Handling"
- added regular particle sampling
- PartioViewer can play sequences
- PartioViewer can write sequences as jpg files
- PartioViewer can generate movies using ffmpeg
- PartioViewer can render rigid body data
- PartioViewer supports multiphase data
- user can now save/load the complete state of the simulation
- bugfixes

- added rigid body export

- added VTK file export (enables the data import in ParaView)
- added file dialog for Windows
- added a Python plugin for Maya to model scenes in Maya and export them to SPlisHSPlasH
- added animation fields to animate particles in an area using a math script
- improved fluid emitters
- added option to simulate without GUI

- added doc files