Create __init__ files

We don't create any init.py files for the generated Python modules to make them a package.

We also need to support the case where there are nested modules. If the output module name is generated._lib.physics.my_calculator then the following files should be created if they don't already exist:

• generated.init.py
• generated._lib.init.py
• generated._lib.physics.init.py

Definitions of done

• Optionally create missing init.py files
• Add option to CLI