Clipboard item deletion is permanent and immediate (without confirmation)

**Is your feature request related to a problem? Please describe.**
When deleting an item from the clipboard history, the item is immediately deleted without any way to get it back (Ctrl+Z doesn't work, and perhaps it shouldn't to avoid being able to retrieve potentially sensitive information).

**Describe the solution you'd like**
When deleting an item from the clipboard history, ask for confirmation to confirm the delete action. For those that would prefer deleting to be immediate (the current behaviour), provide a preference option to enable/disable delete confirmations.

Thanks.