Add purge button to all entities

This page is a capture in the next bucket of the product backlog — a pre-sprint idea, not yet pulled into a sprint as a story.

We should be able to completely trash all data. We probably need a special permission for this but admin should be able to do it. Ideally all entity dialogs should have a purge action.

We should also have a "purge all" button which purges all data from all tables - ignores roles etc. This could be available on the data librarian.