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)!
@nblumhardt I've changed it to use parameters, but I have added a bool option 'useBatchingSink' which defaults to false in order to avoid breaking changes for existing users. Is that compatible with your extension?

@robdmoore I've added an argument check for the batchsize, and set it to use the lowest timestamp for the PartitionKey