Generate model input id attribute based on modelName and attribute

There is a problem when setting `name` attribute explicitly(for whatever reason) on input element like this:
```
echo $form->labelEx($model,'title');
echo $form->textField($model,'title',array('name' => 'someCustomName'));
```

then the generated markup looks like:
```
<label for="Post_title">Title</label>
<input name="someCustomName" id="someCustomName" type="text">
```


therefore clicking on label no longer works (for attribute is different from input id value).

My idea is to generate id attributes of inputs independently of it's name. Just use `model` and `attribute` (see diff), and i get:

```
<label for="Post_title">Title</label>
<input name="someCustomName" id="Post_title" type="text">
```