cosmo_array.in_cgs() returns Comoving quantity when original array was physical

[mladenivkovic]

        data = swiftsimio.load(snapshot_name)
        gas = data.gas
        u = gas.internal_energies

        u_phys = u.to_physical()

        #  print(u_phys[:1])
        #  [1.0279273e-19] kpc**2/kyr**2 (Physical)


        u_phys_cgs = u_phys.in_cgs()
        #  print(u_phys_cgs[:1])
        #  [982.7783] erg/g (Comoving)

        u_phys.convert_to_cgs()
        #  print(u_phys[:1])
        #  [982.7783] erg/g (Physical)
        # ok, this works.

[MatthieuSchaller]

This case will be covered correctly now with the changes proposed to the outputs to handle physical elements better.