Consolidate webserver to just NameNodeAnalyticsHttpServer

[pjeli]

Keeping in line with getting to Apache adoption, the next major refactoring stretch is to remove the old SparkJava webserver and replace it with the Jetty-based NameNodeAnalyticsHttpServer (which is just an extension / minor re-write of the Apache Hadoop NameNode webserver wrapper, NameNodeHttpServer).

This will lessen our codebase and make it even easier to manage.

[pjeli]

The trickiest part of this is validating that SSL and all APIs work exactly the same as the old SparkJava based webserver. So far I have been covering that with unit tests but until I do a swap with an existing instance I cannot validate it safely.