Add Groups for Status Pages#85

Grouping of related monitors and multiple monitors that compose a service can be quite useful for Status Pages. That way there could be an overall availability status of the service and of the individual components if explanded by the user/viewer.

Hello @MPopov , thanks for your suggestion. We already have similar idea in bucket, so I’m merging it. Please, don’t hesitate to comment and vote for the idea that this one is merged to. -> https://uptimerobot.nolt.io/35