* Add path option to SABnzbd component
Adds an optional `path` setting to the SABnzbd component. This allows support for SABnzbd installs that use a different `url_base` (typically a reverse proxied configuration; see https://sabnzbd.org/wiki/configuration/2.3/special).
This change passes the `path` along to pysabnzbd as its `web_root`, which in turn uses the path to build up it's api URLs.
* Use dict.get for Sabnzbd web_root path config