Gear star formation

No need to look at it, I will assign it to you Matthieu when it will be ready.

examples/parameter_example.yml

@@ -338,6 +338,11 @@ EAGLEChemistry:
 
 # Parameters related to star formation models  -----------------------------------------------
 
+# GEAR star formation model (Revaz and Jablonka 2018)
+GEARStarFormation:
+  star_formation_efficiency: 0.01   # star formation efficiency (c_*)
+  maximal_temperature:  3e4         # Upper limit to the temperature of a star forming particle
+
 # EAGLE star formation model (Schaye and Dalla Vecchia 2008)
 EAGLEStarFormation:
   EOS_density_norm_H_p_cm3:          0.1       # Physical density used for the normalisation of the EOS assumed for the star-forming gas in Hydrogen atoms per cm^3.