Added plugin events support to FOFController

You can now implement your custom onBefore/onAfter controller events using system plugins. You will need to create a method named onBefore*component*Controller*view*task*, e.g. onBeforeFoobarControllerItemsRead to handle the onBefore event of com_foobar, items view, read task. Returning false will prevent the task from firing. You can do the same for the onAfter event. Do note that plugin events run *after* the code in your controller and not instead of it or before it. The events must be implemented in system plugins so that they always get loaded by Joomla! before any controller gets the chance to run (remember, HMVC, you may end up calling a controller from a module or plugin).