[key vault] add samples for managing keys, secrets, and certificates

[joshgav]

• [ ] manage keys with Key Vault

• [ ] manage secrets with Key Vault

• [ ] manage certificates with Key Vault

• [ ] deploy certs to a VM for use in serving https web app

• [ ] use secrets in a VM to specify third-party API keys

[mydiemho]

what's the ETA for this? Thanks