Azure: choose resource group name to create multiples cluster inside the same one

[seadiaz]

When I was creating my first cluster on Azure, I could not create it because my application did not have permission to create a new resource group and I realized that kubicorn create a new resource group for the cluster with the same name that the cluster by default.

It will be great to add the capability to set the resource group, thus we could create multiples cluster within the same resource group.

[salaxander]

This seems like it would be a useful feature. I'm happy to work on adding in. I work on Azure so I've got some familiarity there :)