ee/ folder split notes

To support our license scheme, some modules and packages were moved to the ee/ folder found at the top of the repository.

The package references are maintained using the implicit namespace packages from PEP420. __init__.py files were removed for those packages.

IMPORTANT: The Zentral Django apps that are split between the ee/ and standard folders require an explicit path attribute set to the standard folder path. See for example the server/realms/apps.py file.