Updated kubernetes create and kubernetes remove commands

[kanha-gupta]

Fixes #496

PR Summary -

1. Removes --merge and --switch flags. just --save works fine now and fulfills the requirements as mentioned in the issue
2. kubeconfig overwrites have been taken cared of along with making --wait flag implicit while using --save flag
3. Added flag to clear up kubeconfig file for the server that is being deleted. the flag naming is --remove for now. currently it notifies the user if the cluster being deleted is also the current-context so that user performs the needful without any facing any errors.
4. Issue mentioned the need for civo kubernetes update-kubeconfig but I see similar functionality already implemented - civo kubernetes config command. Open to discussion
5. Updated documentation in readme
   Demo ->
   

[kanha-gupta]

@fernando-villalba @uzaxirr please review

[uzaxirr]

Thank you for your contributions, but this has already been implemented.

[kanha-gupta]

@uzaxirr alright, can the community please link PRs to issues so that external contributors know as well and redirect to some other issues ? sometimes it's tough to decipher if a PR exists for an open issue unless we look at code of each open PR :)

Thanks