Provide a command to rename a secret

[PLPeeters]

One thing I find myself doing from time to time is renaming a secret, which is a pain with the current CLI since it requires me to:

1. Fetch the contents of the secret.
2. Create a new secret with the same contents.
3. Delete the original secret.

A kubectl tbac rename secret <new-name> command that does this automatically could come in handy!