Rename BundleInstance to BundleDeployment

[perdasilva]

Instance is a widely used term in programming and from that perspective, having the entrypoint be a BundleInstance create a Bundle could be a cause for dissonance and make the mental model harder to understand. Perhaps BundleDeployment would make it easier to understand and fits well with the k8s Deployment mental model of having a pod spec that creates a pod and a deployment that acts as the top level manager.

[timflannagan]

This seems reasonable to me, although I have no strong opinion here. +1 on the change.

[tylerslaton]

This would definitely help with the confusion some of the initial stakeholders have mentioned with respect to this API. It also clearly points to existing Kubernetes concepts. I am also +1 to this.

[exdx]

This was addressed in #436 -- it's now referred to as a BundleDeployment throughout the codebase