Lot of documentation added (because were missing/wrong and functions modified).
Some change in the code layout (avoiding inline if condition).

[Equil] Enable some print with higher verbose level (were in `if(0){printf(...)}`) and some layout changes.

Most of functions returns an error code

See merge request robotran/mbsysc!350

[Err msg][Ci-skip] updated header file and description

See merge request robotran/mbsysc!385

Merge branch 'MBsysPy_return_error' of https://git.immc.ucl.ac.be/robotran/mbsysc into MBsysPy_return_error

Small stuff

See merge request robotran/mbsysc!384

MBsysPy user vector are in resutls

Closes #242

See merge request robotran/mbsysc!383