Avoid conflicting experiment ids

[kalekundert]

If multiple people are collaborating on a project, they could easily end up creating experiments with duplicate keys. I'll need a way to avoid this. Off the top of my head, one option would be to have each user specify how many users there are, and which user number they are. New experiment ids would be multiplied by the total number of users, then summed with the specific user number. That would work, but requires a lot of manual intervention.