WIP: Go SDK

[yolossn]

[invidian]

Thanks for opening the PR quickly @yolossn! I checked out the code and played a bit with it (though without Nebraska instance) and I produced something like this: https://github.com/kinvolk/nebraska/compare/go-sdk...invidian:invidian/go-sdk?expand=1

The code is likely heavily inspired by Kubernetes Clientset, but I believe it's a decent source of inspiration, as I worked with this client a lot, also from testing perspective and I never really run into some annoyances or limitations. Let me know what you think!

Ah, also sorry for stripping out the actual implementation, but due to time constraints, i didn't have time to restore it, I only wanted code to compile to make sure all types are compatible.

[yolossn]

Hey, @invidian Thanks for the example, the ApplicationClient and GroupClient make sense, unlike adding the NebraskaClient to each object, this method reduces the scope of functions available under each Object.

[yolossn]

@invidian @joaquimrocha I have made the changes based on the comments. At present Applications and Groups are covered, wanted to get another round of feedback before moving to the Channels, Packages, etc. Please take a look.