Merge branch 'isolatedgalaxy' of https://gitlab.cosma.dur.ac.uk/swift/swiftsim into isolatedgalaxy

Conflicts:
	examples/IsolatedGalaxy_dmparticles/angularmomentum.py
	examples/IsolatedGalaxy_potential/angularmomentum.py
	examples/IsolatedGalaxy_potential/isolated_galaxy.yml