Improvement: priority for all participants

[nclaidiere]

When adding participants it would be great to be able to select priority for all of them, rather than 1 by 1 afterwards. This would also solve the problem of having a default priority of 1, which makes the experiment starts immediately for all of them.

[smathot]

Marking this as won't fix for now since it's a feature request rather than a bug fix.

[dschreij]

Let's leave it wontfix for now indeed. I understand this is a valuable addition, but it is a bit tricky to achieve and would require some time to implement.