sets the initial value for a control
rows:[
    { view:"text", name:"country", label:"Country", value:"Belarus" },
    { 
        view:"combo", value:1, options:[ 
            { id:1, value:"Banana" },
            { id:2, value:"Papaya" }, 
            { id:3, value:"Apple" }
        ]
    },
    { view:"button", css:"webix_primary", value:"Submit data"}
]
All controls fall into:
In case of multiple-value controls, the property points to the ID of the initially chosen option.
Value of the control may be: