Add option "Don't use this photo" to Slack training function

[mitchhussey]

As it is now in training, you either have to tell Doorman it was right or train the photo to someone else's face. There should be an option to disregard the photo if it not useful. Examples of when we could have used that include when multiple faces are found (too hard to identify which face it is actually training for), when a picture is blurry, or when it's a picture of the back of someone's head.