Shouldn't use resourcegroup().name in dns labels or storage account names

_From @mmarch on March 6, 2017 20:15_

This always leads to validation errors - dns names and storage account names cannot have uppercase letters or dashes '-'.

See Azure/azure-quickstart-templates [Issue #2990](https://github.com/Azure/azure-quickstart-templates/issues/2990), and #12.

Per [Best Practices guidelines for Resources: domainNameLabels](https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-manager-template-best-practices) should use uniquestring(resourceGroup().id) instead in all cases.

_Copied from original issue: mmarch/rds-templates#35_