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'.

use chunked mappers in the threadpool, make sure that the map function actually waits for all the threads to have started.

Commented out, note gparts test is unchecked.

When moving foreign particles to the end of the list, make sure we don't swap with one that is a foreign particle.