Compute the total mass in the system and add a variable to the gpart to record how much mass they interacted with via self-gravity.

Added the option to replicate the particles along the axis to create artificially larger test cases. Driven by the parameter 'InitialConditions:replicate'.

Added an (expensive) debugging check to verify that all cells have been drifted to the current point in time before a rebuild or a repartition.

Don't pass the cell_min as an argument to space_rebuild(). Just use the value stored in the space structure.

This depth is way beyond our precision.

First initalisation of particles now happens in space_init() and not in engine_init_particles() any more.

Renamed 'h' in cell struct to 'width' and renamed 'h' and 'ih' in the space struct to 'width' and 'iwidth'.