Use a single global value for the current runtime, this should avoid issues with the exact timing of when the limit is exceeded

Backport a fix from the COLIBRE repo to solve a segfault in the cleaning routines when ending a run that restarted from check-point files.

Revert "When dumping a restart file at the end of a run, only drift the particles if no other form of i/o has taken place this step to avoid a drift towards the past."

This reverts commit d93c56e9.

When dumping a restart file at the end of a run, only drift the particles if no other form of i/o has taken place this step to avoid a drift towards the past.

Make gravity dithering the default behaviour. Put the variables in the gravity properties for consistency.

In the case where the gas particles are generated from the ICs, set 'with_baryon_particles' to 1 as well.