Add support for qBittorrent

[vt0r]

Received our first App Store review, and it's got a feature request for supporting qBittorrent.

I don't have it installed, but I can get a container running to test against.

The API docs look solid: https://github.com/qbittorrent/qBittorrent/wiki/WebUI-API-(qBittorrent-5.0)