Desktop menu

It builds a *~/.config/menus/applications-menu.config* file with include/exlcude preferences of desktop.files
TODO: to provide some intelligence to detect cinnamon or lxde

Dependency: xdg-ruby gem. Source code: https://github.com/gecos-team/ruby-xdg 

```json
{
    "run_list": "recipe[gecos_ws_mgmt::default]",
    "gecos_ws_mgmt": {
        "users_mgmt": {
            "desktop_menu_res": {
                "users":[
                    { // Esto genera fichero ~/.config/menus con directivas Include/Exclude
                        "username": "vagrant",
                        "desktop_files_include": ["caribou.desktop"],
                        "desktop_files_exclude": ["firefox.desktop", "opensc-dnie.desktop"]
                    },
                    { // Esto genera fichero ~/.config/menus con directivas Include/Exclude
                        "username": "vagrant",
                        "desktop_files_include": [],
                        "desktop_files_exclude": ["firefox.desktop", "opensc-dnie.desktop"]
                    },
                    { // Esto elimina el fichero para restaurar configuración original
                        "username": "vagrant", 
                        "desktop_files_exclude": [],
                        "desktop_files_include": []
                    }//,
                    //{ Esto fallaría: fichero .desktop no presente en el sistema
                    //    "username": "amian",
                    //    "desktop_files_include": ["evince.desktop"],
                    //    "desktop_files_exclude": []
                    //},
                    //{ Esto fallaría: usuario que no existe
                    //    "username": "usuario_que_no_existe",
                    //    "desktop_files_include": [],
                    //    "desktop_files_exclude": []
                    //}
                ],
              "job_ids":["1","2"]
            }
        }
    }
}
```