More naming convention improvements in the EAGLE cooling section of the YAML file.

doc/RTD/source/SubgridModels/EAGLE/index.rst

examples/CoolingBox/coolingBox.yml

examples/CoolingRates/cooling_rates.yml

examples/EAGLE_12/eagle_12.yml

examples/EAGLE_25/eagle_25.yml

examples/EAGLE_50/eagle_50.yml

examples/EAGLE_6/eagle_6.yml

examples/SantaBarbara/santa_barbara.yml

examples/SmallCosmoVolume_cooling/small_cosmo_volume.yml

examples/parameter_example.yml

src/cooling/EAGLE/cooling.c