Menu Editable: Create context menus for gtkeditable widgets

This class creates context menus to associate to gtkeditable widgets of PHP-GTK graphical user interfaces.

These menus usually appear when the user clicks on the right mouse button when the pointer is over the editable widget.

The class provides a common menu with the functions to cut, paste, copy, delete, select all and cancel. When the user clicks on these menu items, the class invokes the corresponding action methods of the editable widget.

The class also provides the icon images that are used in the context menus. These images are defined within the class using text strings.