[Feature Request] Suggestion for optimizing form validation

### Existing Component
Yes

### Component Name
Form

### Description
It must set the `prop` attribute to `el-form-item` component to make validation work. Like this:
```

```
I think `prop` attribute and `model` attribute are needless. It's more intuitive if we make this work.
```

export default {
data () {
return {
rules: { name: { required: true, message: 'name is required' } }
}
}
}

```