Feature Request: Select all subscriptions

I didn't find a previous request for this. I'd like to see a Select All button added to the Subscriptions page. It is quite tedious to have to click a hundred or more individual topics to unsubscribe to (which I just had to do since I was being inundated with e-mail).

It should be pretty straightforward to add this feature, since it's only necessary to add a javascript to run through the array of checkboxes and set them to true.

Then if there are a few someone wants to keep, it's much easier to just unselect them and delete the rest.

Thanks very much!