Add support for KV v2 "destroy" command

[adam-farhi]

https://developer.hashicorp.com/vault/api-docs/secret/kv/kv-v2#destroy-secret-versions

from what I saw in the commands, it's not available.
https://github.com/nodevault/node-vault/blob/master/src/commands.js

[delfuego]

I mean, unless I'm mistaken, node-vault still has no support for the v2 KV engine.

[intelline]

i need that one also, probably we can create a PR with the ready code?

[aviadhahami]

@intelline if you could PR this that'd be great :)