[Libcloud-556] Azure Compute Driver Support

We have completed support for the Azure compute driver. This adds support for the core compute driver functions against Azure. The JIRA ticket can be found here: 

https://issues.apache.org/jira/browse/LIBCLOUD-556?jql=project%20%3D%20LIBCLOUD

Let me know if there are any issues or if it can be accepted or not. 

Thanks. 
-matt