Starts a global plugin running.
If the plugin was previously active then calling
start will reset it to an active state and then
If the plugin has never been run before a new instance of it will be created within the Plugin Manager,
its active state set and then both of its
start methods called, in that order.
If the plugin is already running under the given key then nothing happens.
The key of the plugin to start.
Run the plugin under a new key. This allows you to run one plugin multiple times.
The plugin that was started, or
null if invalid key given or plugin is already stopped.