Implemented collection of resource stats for Windows Azure SQL Database.

A couple of months ago a new dynamic management view was added to Windows Azure SQL Database. This view (resource_stats) contains some central performance metrics for the databases. For example, it allows you to see how many CPU cores you currently use. 

If you purchase Windows Azure SQL Database Premium Edition, you get reserved resource (for example 1 CPU core) and this commit allows you to see how much of these resources you actually used. We've been recommended by Microsoft to continously monitor the resource_stats, so I thought that adding it to the New Relic plug-in would be a good idea. We are currently running these changes in preview in our own production.