- 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.

Resolve "BlockForest::saveToFile/loadFromFile not working in single precision"

Closes #20

See merge request !25

Resolve "BufferSystem used in master-slave mode"

Closes #21

See merge request !30

Squirmer VTK output

See merge request !27

Silence conversion warning in quaternion

See merge request !28