Addde volume example
passthrough model material
examples for center of mass tests
Remove find_cuda.cmake.

It's not needed anyway.
Merge branch 'release/v0.4.0'
Use custom FindBullet.cmake.
Change version number.
Merge branch 'release/v0.4.1'
no building examples
Merge branch 'develop' into feature/new_physics
always link guacamole-physics in build
example verions with physical geometry loader