Diagnostics: better visibility into system failures

[michaelisard]

User code errors are transmitted reasonably well through the job logging, but system failures tend to get discarded by the YARN logging. Need a way to selectively copy failure logs into Azure.

[fetterly]

I updated the documentation to include the command line for dumping the logs using the YARN command line utility. On HDInsight clusters, this is yarn logs -applicationId <APPLICATION_ID> -appOwner <CLUSTER_USER_NAME>.