add new "overspin_algorithm" option to handle what happens
when a star is spinning faster than it can
currently there are two options:
OVERSPIN_BSE transfers the excess angular momentum back to the orbit,
so is conservative in that no mass or angular momentum is lost.
OVERSPIN_MASSLOSS uses the rotationally_enhanced_mass_loss formalism
given below to remove material which reduces the star's spin.
Also removed the ROTATIONALLY_ENHANCED_MASS_LOSS compile define,
because this functionality is now required always.
Added GAIAHRD logging flag for (currently, probably always, incomplete) Gaia logging.
Update stellar colours to use "magnitudes" rather than "colours" because this si more complete nomenclature.