Add Dependencies#78

I would be nice to have dependency alerting. If I monitor 25 websites internal to my company and our primary firewall or internet connection goes down, I don’t need 25 alerts on 25 sites. If our primary connection goes down ‘nothing’ will be accessible. Being able to setup dependencies would resolve this. all 25 websites would be dependant on the device ‘above’ it to be accessible.

To extend to this, it would be nice if it allowed for dynamic alerting. I want to know that there is an outage but getting 25 copies of alerts simultaneously is chaos. If root monitor is down then send summary alert for root including sub monitors

I believe this should be merged with Ability to Compile Uptime Notifications into One Message#129 as they both expect the same result.