Correct use of caches in the self-PP gravity task. Make sure we can run without vectorization. Make sure we can run without hydro.

Do the P-P gravity calculations in the frame of the cells for more accuracy in the distance calculations.

runner_dopair_grav() should abort if the distance between the cells is larger than the mesh smoothing scale.

Split the gravity pp tasks into truncated and full Newtonian potential. Use the full potential when the particles are close enough.

Added a parameter to the gravity properties to contain the distance below which all computed forces are Newtonian

Make the long-range gravity task escape the cells that are beyond the range handled by the mesh forces.

runner_dopair_grav_pp() can now use the periodic boundary conditions. The L2L kernel is now always non-periodic as the shift should never cross a domain boundary.

Create the gravity pair tasks over the periodic boundary conditions. Make the long-range gravity task loop over the cells even over the periodic boundaries.

runner_dopair_grav_pp() can now use the periodic boundary conditions. The L2L kernel is now always non-periodic as the shift should never cross a domain boundary.

Create the gravity pair tasks over the periodic boundary conditions. Make the long-range gravity task loop over the cells even over the periodic boundaries.

runner_dopair_grav_pp() can now use the periodic boundary conditions. The L2L kernel is now always non-periodic as the shift should never cross a domain boundary.

Create the gravity pair tasks over the periodic boundary conditions. Make the long-range gravity task loop over the cells even over the periodic boundaries.

runner_dopair_grav_pp() can now use the periodic boundary conditions. The L2L kernel is now always non-periodic as the shift should never cross a domain boundary.

Create the gravity pair tasks over the periodic boundary conditions. Make the long-range gravity task loop over the cells even over the periodic boundaries.

Branch to a different, more accurate, calculation in the long-range that don't match the MAC any more.