Implement "factory reset"

I am not sure, whether this is the right repository for this, but I would like to keep track of an enhancement proposal that I have been thinking about for a while now.

I think it would be extremely useful to have a "factory reset" button, that would allow users (and administrators), to reset the AiiDAlab environment to "factory conditions", that means basically that the environment is completely reset. Use cases include, but are not limited to:

1. The ability to test the "new user" experience, especially for testing and in preparation for workshops etc.
1. The ability for users to reset their environment after having it rendered inadvertently unusable in some way.