Fix #588 - Refactor plugins.

- Added settings.py with PluginConfig.
- Rewrote jackaudio's load_init()
Yes, this method of searching for firewire devices isn't good but is good enough in most cases. Ideally we should actually be using the same way we do with USB where we ask some sort of API for what exists on the system. No one's done any research on how to get this information for Firewire devices though so that's why we have the current method.