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

Multiple blocks per process with createUniformBlockGridFromConfig

See merge request !35

Remove useWorldComm from createBlockForestFromConfig

See merge request !33

Resolves an MPI Abort Error that will reliably happen.