Launcher: add JustType launcher management

 * move JustTypeField together with the rest of the Launcher components
 * add a JustTypeLauncher component, dedicated to contain the justtype launcher window
 * add the management of the WindowType.Launcher window type
 * add missing pieces to the Test objects to be able to create a fake JustType launcher


Signed-off-by: Christophe Chapuis <chris.chapuis@gmail.com>