Add support for <cinder type-list> and <cinder create --volume-type>

Added support for volume types
I'm currently running this with Python 2.7.6 as well and am not getting any error when removing the \n and \r replacements...

```bash
$ python -V
Python 2.7.6
```

Does this work for you? If not, what is the error?
```python
>>> import json
>>> json.__version__
'2.0.9'
>>> json.loads(open('etc/volume_types.json').read())
{u'volume_types': [{u'extra_specs': {u'drivers:san_backed_disk': True, u'drivers:exact_capacity': False, u'capabilities:volume_backend_name': u'sjc01', u'drivers:display_name': u'default'}, u'id': u'241', u'name': u'san'}]}
>>>
>>> open('etc/volume_types.json').read()
'{\n    "volume_types": [\n        {\n            "id": "241",\n            "name": "san",\n            "extra_specs": {\n                "capabilities:volume_backend_name": "sjc01",\n                "drivers:display_name": "default",\n                "drivers:san_backed_disk": true,\n                "drivers:exact_capacity": false\n            }\n        }\n    ]\n}\n'
```