Provide a resend confirmation action link for invoices

Attached a screenshot of what the action link looks like. Note that I added a "Download" action link as well.

Note that I'm altering the label() method to have consistent labels accross the UI.

The scope expanded... I'm hoping I'm not making a mistake by overridding the label() method but I think this change makes sense and is kind of similar to what was done for orders (although we don't use the type there).