Add some implicit tasks to walk the tree up and down after the multipole initialisation and before the downpass.

Matthieu Schaller authored May 23, 2018 and Matthieu Schaller committed Jun 18, 2018

Extract the mesh gravity forces to a separate set of functions. Get the forces directly from the mesh to the gparts. Do not use the tree here.

Re-introduce the 'end_force' function as a task in order for the cooling function to be called at the right place in the time-step.

Made the ghost_in and ghost_out a separate task type to stop the confusion of the ghost being sometimes implicit.

Don't lock the tree for the grav_init task. Don't call the unsorted pairs at all. Skip the entire zeroing loop when no xparts in runner_do_sort()