Plugin Daemon interface.
Daemon plugin are automatically loaded when the application is started.
Icy will always execute them in a separate thread for safety so the interface extends
They can be enabled / disabled from the Icy preferences window.
Called by Icy to stop the daemon plugin.
After this method has been called, the run() should terminate.
The method is also used to "uninitialize" plugin (unregister listeners).
This method is synchronous and should not consume too much time.