Batch Explorer code sample update

The [Azure Batch Explorer code sample](https://code.msdn.microsoft.com/Azure-Batch-Explorer-c1d37768) is updated to use the latest Batch client library. * Batch Explorer options are persisted to disk so it will survive a process restart. * Batch account and key are encrypted before saving to disk. * New work item view combines work items and the job list. The performance is much better for large work items, large job collections, or slow Internet connections. * There were minor bug fixes regarding task and virtual machine file views. An introduction to Azure Batch Explorer can be found on [The Microsoft HPC & Batch Team Blog](https://blogs.technet.com/b/windowshpc/archive/2015/01/20/azure-batch-explorer-sample-walkthrough.aspx). * Batch * SDK and Tools * [ Batch](https://azure.microsoft.com/en-gb/services/batch/)