ACK and mute alerts for a specified duration

Possibility to ACK any single alert and hide future alerts for that device+alert_rule-combination for a specified duration. Option should probably be visible on ACK-modal and the option to allow this should be user configurable.

One way to implement this might be to just automatically ACK any new alerts that match this condition with the ACK-message from the original muting ACK, display a clear sign that this new alert is on alerted state but it is muted and has a note. Also, transports should be disabled for the specified duration.