Better level for the time-step limiter task to make sure the gravity and hydro steps are synchronized.

Put the FPE check back in for now. There might still be unexpected problematic side cases that need special treatment in the enrichment routine.

Small enrichment fixes

See merge request !940

Protect the feedback from 0 ngb stellar evolution and allow a lower thermal energy after enrichment because it can physical happen

Mpi memory clean

Closes #619

See merge request !936

Clarify box_wrap

See merge request !939

Parco 2019 debug

See merge request !930

Make the minimal SPH scheme collect the minimal time-bin of the neighbours in the force and use this when setting the time-step size.