add a way to acknowledge option

[ivukotic]

There are issues that we know about but can't fix. We need a button to acknowledge these.
Once acknowledged alarms will be made but alerts won't be sent to anyone.
Alarm acknowledging would use a subset of variables in "source" field for matching. The subset will be give in variable "acknowledge_matching" field in {{host}}/alarm/category

Acknowledgements should be stored and displayed on the web site (who did it, when, etc.)