Add function to query cluster's API version

[clstokes]

Problem description

There is not currently a way in the Kubernetes SDK to query for the Kubernetes cluster's API version - e.g. 1.14, 1.15, 1.16, etc.

Suggestions for a fix

Provide a function getApiVersion() (or more appropriately named) for users to query their cluster's API version and use as part of their application.

[farvour]

I am actually quite disappointed that this isn't available. At the very least, the provider should provide a way to invoke lower-level client calls from the client-go library. Since we're using Python SDK, it looks like I get to use the kubernetes module and do it myself.... :(