Do not change original data by kv.group

Do not patch isValid, errors and isAnyMessageShown to original given data
```javascript
ko.validation.init();

var data = {
    first_name: ko.observable('John').extend({required: true}),
    last_name: ko.observable('Doe').extend({required: true}),
    email: ko.observable('john.doe(at)example.com').extend({required: true, email: true}),
};
var validatedObservable = ko.validatedObservable(data);
var normalObservable = ko.observable(data);

validatedObservable.isValid();
validatedObservable.errors();
validatedObservable.errors.showAllMessages();
validatedObservable.errors.isAnyMessageShown();
ko.toJSON(validatedObservable()); // {first_name: "John", last_name: "Doe", email: "john.doe(at)example.com"}
console.log(ko.toJSON(validatedObservable()) === ko.toJSON(data)); // true
console.log(ko.toJSON(normalObservable()) === ko.toJSON(data)); // true
console.log(ko.toJSON(validatedObservable()) === ko.toJSON(normalObservable())); // true
```

removed
```javascript
validatedObservable().isValid();
validatedObservable().errors();
validatedObservable().isAnyMessageShown();
ko.toJSON(validatedObservable()); // {"first_name":"John","last_name":"Doe","email":"john.doe(at)example.com","errors":["Please enter a proper email address."]}
```