Release re-factored provider based on https://github.com/hashicorp/terraform-plugin-go.

This release brings some very significant changes and improvements.
Most importantly, planning no longer relies on API dry-run calls but instead creates a completely typed resource based on the Kubernetes OpenAPI definitions.
Among other things, this allows multiple dependent Kubernetes manifests to be applied in the same operation (not including cluster stand-up).