CDK-604: Added commands to generate logging and Flume configs

* The Flume configuration defaults to an AvroSource listening on 0.0.0.0:41415
* The Flume configuration defaults to a file channel
* The log4j configuration defaults to writing to port 41415, but requires the hostname
* The log4j configuration requires a package or class name to log to Flume, or a
  switch of --log-all to configure the rootLogger.
* Besides the unit tests, I ran some manual tests on a cluster by completing the
  logging example, but using the tool derived configs rather than the ones that
  shipped with the example.
I don't agree these are just for demo purposes. They don't expose _every_ option, but they expose more than enough that you could use these to generate a Flume configuration that you could put right into production.

I can see the value in generating commented out configuration options with descriptions for things that don't need to be set very frequently, but I think it's a mistake to require that users edit the configuration files that we generate. If all we care about are demos, then we could keep shipping the pre-existing configuration files in the demos like we do today.