add management command to create fake comments

[goapunk]

Describe your changes
Add a management command to create fake comments on an idea

testing: create an idea collection module, add an idea, get the id/pk from the django admin (i.e. http://127.0.0.1:8003/django-admin/meinberlin_ideas/idea/). To create one comment as the admin user run python manage.py create_comments --user 1 --idea <the id of the idea you just looked up> --count 1

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