Gets a global plugin from the Plugin Manager based on the given key and returns it.
If it cannot find an active plugin based on the key, but there is one in the Plugin Cache with the same key, then it will create a new instance of the cached plugin and return that.
The key of the plugin to get.
Automatically start a new instance of the plugin if found in the cache, but not actively running.
The plugin, or
null if no plugin was found matching the key.