Adds Token-based Auth

This adds the ability to use username/password based auth to get an auth token to use for subsequent calls.

```python
import SoftLayer
client = SoftLayer.Client()
client.authenticate_with_password('username', 'password')

import SoftLayer
client = SoftLayer.Client()
# Get all security questions (you can basically pick one at random that you is answered for the user)
client['User_Security_Question'].getAllObjects()
client.authenticate_with_password('username', 'password', 122, '2004')
```


This is waiting for an API release to add this feature to the XML-RPC API.