Lotsa things: a Priority class to deal with priorities, an Event class to shape an event, an EventManager class to gather all the events and trigger them
Added the initialization of the _addons property to the SiteDispatcher class and a tweak to the allowed controller names that I may need i nthe future :P

Signed-off-by: emanuele <emanuele45@gmail.com>
Move post/attach error objects from variable to class properties (could break stuff)
Do not ask for returns, just count the initial number of possible mentions and what is left at the end
Missing path in autoloader
The pre_dispatch should be called when we are sure what is the action we want to do
Separate the registration of addons that is slighty particular (it requires a static method)
Fix the Template_Layers class when errors occur
Converted the display of mentions in Mentions_Controller to the events system (lost backward compatibility and removed integrate_add_mention hook) + typos