Add a template for classic projects

[pbauer]

We want to have as little duplication as possible, so I wonder if it is possible to create a template project_classic that calls the main project template but hides some questions (e.g. volto_version, frontend_addon_name) and changes other settings (e.g. set __feature_headless to "0").

After creating the project a hook could delete the /frontend folder and some files in devops and the main Makefile would need to be replaced.

[davisagli]

I don't think it's possible the way cookiecutter works currently. The questions are defined in cookiecutter.json which lives inside the template directory. Possibly things could be refactored so that both project templates run a shared subtemplate.