Add select all checkbox in the Existing Backups table

[dynamiccookies]

It should only be available when the trash can icon isn't available. This means when the checkbox is clicked, in addition to selecting all the checkboxes in the table rows, it will also need to hide itself so the trash can icon can appear.

[dynamiccookies]

The problem with this is then you can't uncheck everything. Need to think about it.