Added batching sink for Azure table storage

Hi I've added a batching sink for Azure Table Storage using your base class. Cheers for the ace project(s)!
`TableBatchOperation` has two limitations that we need to take into account - the batch size must be no more than 100 and all of the items being saved must have the same partition key.

http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.storage.table.tablebatchoperation.aspx