Make AzureReader2 depend on Microsoft.Azure.Storage.Blob

[ajbeaven]

As per the description of the WindowsAzure.Storage nuget package, as of version 9.4.0, WindowsAzure.Storage has been replaced by multiple packages.

AzureReader2 should now depend on Microsoft.Azure.Storage.Blob.

[lilith]

Thanks!

[lilith]

We can't do this until we require .NET 4.7.2 or higher, so marking this as a v5 task