Allow admin users to duplicate `Experiment` objects from admin interface

[BeritJanssen]

After #1135, the form to create an experiment will be even longer than prior to the refactor. To simplify creating an experiment which is virtually identical, apart from a questionnaire of playlist, it would be a nice feature to add an action from the dropdown menu in the admin interface, which creates a copy of an existing experiment, in which the slug is automatically modified to, e.g. {original-slug}-copy.

Requirements

• Add copy/duplicate button to Experiment section in admin interface
• Clicking the duplicate button will copy the Experiment and give it a:
  • Name: {original-name} (copy)
  • Slug: {original-slug}-copy
• Additionally, it will copy the related:
  • Phases
  • Blocks related to the Phases
  • ThemeConfig related to Experiment & Block, along with its HeaderConfig & FooterConfig
  • Feedback related to the Blocks?
  • QuestionSeries related to the Blocks?
  • SocialMediaConfig

[drikusroor]

What do you mean by "virtual identical, apart from a questionnaire of/or playlist"? Does that mean the duplicate Experiment will have no playlist? Or will the playlist be duplicated as well? Perhaps it would be good to have a list of properties / fields that will or will not be duplicated along with the Experiment.

[BeritJanssen]

These are choices I have not thought about enough. In general, I think the only reason to duplicate an experiment without modifying the questions or playlists would be to add a different Consent form (e.g., you relaunch the experiment but with different contact persons), so perhaps we could even choose to copy everything but the Consent form.