[SPARK-2411] Add a history-not-found page to standalone Master

Right now, if you click on an application after it has finished, it simply refreshes the page if there are no event logs for the application. This is not super intuitive especially because event logging is not enabled by default. We should direct the user to enable this if they attempt to view a SparkUI after the fact without event logs.

Here is what the new page looks like:

<img src="https://issues.apache.org/jira/secure/attachment/12655082/Master%20event%20logs.png">
I mean that if the are joining an existing cluster, they'll need to figure out what HDFS or FS path to set this too such that it's consistent with the path set by the person running the history server.