validates one record or all dataset against the validation rules
| id | string | the id of the record to validate | 
| boolean | true, if the record is valid | 
mygrid = webix.ui({
    view:"datatable",
    columns:[
        {id:"rank", header:"", width:50, editor:"text"},                
        {id:"title", header:"Film title",  width:200, editor:"text"},        
        {id:"votes", header:"Votes", width:100, editor:"text"}
    ],
    rules:{
        "rank":positiveNumber,
        "votes":positiveNumber
    }
});
 
/*validate all records*/
var result = mygrid.validate();
 
/*validate first record*/
var result = mygrid.validate(mygrid.getFirstId());
If the id was not provided, the component will validate all records.
The method uses config.rules for validation.
Invalid rows are displayed with the "webix_invalid" marker.