RFC - Azure Resource Manager support

In November 2015, Michael Richardson discussed a significant shift in Azure's resource management from Azure Service Management (ASM) to Azure Resource Manager (ARM), highlighting the implications for Octopus Deploy, which at the time interacted only with ASM. To support ARM, proposals included adding a new Azure Service Principal account type requiring Azure Active Directory authentication, and introducing a "Deploy Azure Resource Group" step for provisioning resources using JSON templates, which could dynamically adjust parameters based on various conditions. The proposed changes aimed to streamline the deployment process, allowing for validation against ARM to ensure JSON template correctness before deployment. Additionally, Richardson mentioned considerations about integrating templates from a Git repository and the gradual phasing out of Service Management API development by Microsoft, which underscored the growing importance of adapting to ARM for future Azure deployments.