sets a label for the left list
webix.ui({ 
    view:"dbllist", 
    value:"1,2", 
    labelLeft:"All groups",
    labelRight:"Selected",
    data:[
        {id:"1", value:"Contacts"},
        {id:"2", value:"Products"},
        {id:"3", value:"Reports"},
        {id:"4", value:"Customers"},
        {id:"5", value:"Deals"}
    ]
});