feat #1173 Input field focus on label click

This pull requests allows the focus to be set on input field whenever user clicks on the label for all the input based widgets
If we provide just the function `this._onLabelClick`, the listenere won't be removed. The whole object that was used to add the listener has to be used:
```
{
    fn : this._onLabelClick,
    scope : this
}
```