EE version: Clean up the Project model to reduce conflicts

Merged yorickpeterse-staging requested to merge ee-clean-up-project-for-merge-conflicts into master

This is the EE version of MR It includes the changes of said MR along with moving all EE specific code (except for some include / prepend calls) to separate concerns. This should ensure the model is almost identical for both CE and EE, reducing the number of merge conflicts.