- normal CMake Python search can be used if the python interpreter is
  searched before the searching the libraries

Not all timer names are gathered, a parallel set reduction is used instead

Fixes for CUDA on Windows

See merge request !39

- nvcc also printed warnings in system libs like boost

FindCUDA apparently can't handle CMake "generator expressions"
these are removed before calling FindCUDA and restored afterwards

- nesting check macros in iteration macros not working

- default python is the one reported by python3-config

 function was apparently never used

second tutorial added
updated older tutorials
made tutorials also tests

Resolve "Reusable body dispatcher"

Closes #22

See merge request !29

Switchable integrator and contact resolution for DEM

See merge request !32

Add user ID to sphere VTK output

See merge request !38