Added function get_config() - ownCloud config information

It's just a function to get ownCloud config information - returns JSON, e.g.:
{'website': 'ownCloud', 'ssl': 'false', 'host': 'cloud.example.com', 'version': '1.7', 'contact': ''}

Btw, please delete previous pull request as it was not complete.
Just as a note: when using OCS API you can also make it return JSON by passing `format=json`.
I still haven't decided whether it's better to parse the XML result or JSON.

Anyway, this looks good so ignore my comment :smile: