Feature Request: Give config file and credentials

Hi,

in the CLI-version of openvpn it is possible to pass a config file and credentials:
```batch
openvpn --config ".\server.ovpn" --auth-user-pass ".\credentials" --auth-nocache
```

In `credentials` (line 1+2)
```
username
password
```

Is it possible to put this into the API?