Merge branch 'RTD_updates' into 'master'

doc/RTD/Makefile

doc/RTD/README.md

doc/RTD/source/GettingStarted/compiling_code.rst

doc/RTD/source/GettingStarted/configuration_options.rst

doc/RTD/source/GettingStarted/running_example.rst

doc/RTD/source/GettingStarted/running_on_large_systems.rst

doc/RTD/source/GettingStarted/special_modes.rst

doc/RTD/source/GettingStarted/what_about_mpi.rst

doc/RTD/source/InitialConditions/index.rst

doc/RTD/source/ParameterFiles/parameter_description.rst

doc/RTD/source/RadiativeTransfer/RTTaskDependencies.webp

doc/RTD/source/RadiativeTransfer/RT_notes_for_developers.rst

...RTD/source/RadiativeTransfer/full_dependency_graph_RT.dot

doc/RTD/source/RadiativeTransfer/make_graphs.py

doc/RTD/source/SubgridModels/AGNSpinJets/plots.py

doc/RTD/source/SubgridModels/AGNSpinJets/theory.rst

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

doc/RTD/source/SubgridModels/EAGLE/plot_EAGLE_SF_EOS.py

doc/RTD/source/SubgridModels/EAGLE/plot_EAGLE_SF_Z_dep.py

...TD/source/SubgridModels/EAGLE/plot_EAGLE_entropy_floor.py