Option to delete all past passes

[simontb]

I think an option that deletes all passes with events that are in the past would be useful. Flow could be like this:

1. Click 'Delete past passes'. (I don't know yet where to place this option)
2. The directory is searched and all past passes (or their IDs, I'm not familiar with the store, yet) are loaded.
3. A pop-up is displayed 'This will delete n passes. Do you want to proceed?'.
4. Click on 'Yes' deletes the passes, click on 'No' aborts deletion.

What do you think? Especially feedback where to place that option would be useful.