title: DownloadRangeToByteArray method in CloudBlockBlob
body: <p>I'm using Azure SDK v2.1.0.0. I found a method in CloudBlockBlob class called DownloadRangeToByteArray, but unfortunately I can't find any documentation about it in the online MSDN?</p>
  
  <p>any idea about it's usage, constraints, thread safety?</p>