- removed AntTweakBar GUI

- added imgui
- added PLY export
- added documentation of scene file format

- added XPBD FEM constraint for deformable solids

- updated to Eigen 3.4.0

Merge pull request #114 from InteractiveComputerGraphics/python_bindings

Python bindings

- added substepping

- added OBJ export

- added DamperJoint

- improved implementation of SliderJoint
- improved implementation of TargetPositionMotorSliderJoint
- improved implementation of TargetVelocityMotorSliderJoint
- improved implementation of HingeJoint
- improved implementation of TargetAngleMotorHingeJoint
- improved implementation of TargetVelocityMotorHingeJoint

- added collision detection for arbitrary meshes based on cubic signe…

…d distance fields

- added Discregrid library as external project to generate cubic signed distance fields

- bugfix

- updated README.md

- added TargetVelocityMotorHingeJoint

- added TargetAngleMotorHingeJoint
- extended JointDemo
- made function names consistent

- added documentation