[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">
Should you also mention the setting for the event log directory? Otherwise they might think they can just set `enabled` and it will auto-magically work.