Collections keep their promises

A round of fixes to what collections actually do. Raising a collection's scope to comprehensive now deepens the members it already holds, instead of only the ones you add afterwards - so a collection that says it captures battles captures them. Deleting a collection now stops the recordings it was the only reason for, rather than leaving them running for a list that no longer exists. And two roster edits arriving at once no longer overwrite each other, so an add can never quietly drop somebody another add just put in.