Code cleanup for Kubernetes Client

[mccheah]

org.apache.spark.deploy.kubernetes.Client is just over 800 lines long. Find a way to break it down into multiple classes that each handle a different aspect of submitting to Kubernetes. One aspect could be the watches and readiness, for example. Another could be configuring SSL.

[foxish]

@mccheah Do we want to do this before we cut the alpha release?

[mccheah]

Don't think so - would be a pretty significant change. Let's release what we have as the alpha (or something close to it) and we can refactor + harden it after the fact.

[foxish]

Agreed. Marking this as beta.

[mccheah]

Moving to alpha since we'd like this to get #110 into alpha as well.

[foxish]

This item is done I think
@mccheah

[mccheah]

Sort of - I'm going to close this for now, it's a little vague and we can break it down more granularly, and the different cleanups can be done over time. This has everything I eventually want though, at least from my current perspective: #184