quick_frontend (menus): added a quick_menus module to manage easily menus logic: - there are 2 mains types of menu: MenuItem which can be launched, and MenuCategory which contains other menus - local menus (from frontend only) and distant menus (from backend and its plugins) are managed - there is a menu manager which, in a similar ways as for widgets, manages the menus logic and should be instantiated by host - when a context is necessary (this is the case for most of menus), a data collector is used: it collects data from the caller (the instance linked to the menu) and construct data which is then sent throught bridge - to have implementation specific to a frontend which override the backend one, there is a MenuHook class - it is possible to place an expected menu in the desired position with MenuPlaceHolder class