In the black hole interactions functions, added a loop over BH pairs that is only activated in the case of swallowing/merging.

Fix missing factor of h^3 when computing the BH swallowing probability in EAGLE's runner_iact_nonsym_bh_swallow()

Implement the reduction of the accretion rate of the BHs based on the local viscuous time-scale in the EAGLE model.

Do not force the star particle to be a constant in the default feedback model. This is used for debugging.

Force an emergency re-sorting of all the star particles below a given super cell when star formation happens.