Ability for 'az deployment group create' command to automatically create the specified resource group if it doesn't already exist

When testing ARM templates, a very common pattern is to create a resource group and then immediately deploy the template into it. Currently this requires two steps:

az group create -n MyResourceGroupName -l location
az deployment group create -g MyResourceGroupName -f template.json

It would be great if we had a single step operation to do both of these. Please consider adding the ability for the `az deployment group create` command to create the resource group if it doesn't already exist. Perhaps a new `--create-group-if-not-exists` flag could be added?