Add more comments to the starformation.h file and include the engine in the star_formation_convert_to_star

Add additional arguments to the star formation function such that we can use the function cooling_get_temperature()

Make the starformation more general for other models than the EAGLE model and make the Schaye (2008) star formation such that it works with that

Make the starformation more general for other models than the EAGLE model and make the Schaye (2008) star formation such that it works with that

Added mechanism to add tracers information to the xparts. Added the EAGLE tracers (max(T) and time of max(T)). Tracers are dumped in snapshots.

Use the same naming convention for the hydro sort activation function and the star sort activation function.