Change label 'for' to point at field id

formly produces markup something like this (simplified):

```
<label for="email" class="control-label">Email address</label>
<input id="field_email" type="text" name="email" value="">
```

However, the 'for' attribute on the label should be the 'id' attribute of the related input field, not the 'name' attribute. ie, in this case, it should be:

```
<label for="field_email" class="control-label">Email address</label>
<input id="field_email" type="text" name="email" value="">
```

Then when you click on the label, the input field gets focus. 

Awesome bundle, BTW. Does everything I need, simply and cleanly.