Confirm mixin
    
    Base mixin class for dialogs witch confirmation/canceling capabilities.
    
    When used, dialog can be 'confirmed' by 'enter' key or canceled by 'escape' key. It doesn't accept confirmation from all elements to not override default expected behavior like creating new line in text area, executing link or selecting a value in a select element.
    
    https://fedorahosted.org/freeipa/ticket/3200