Exposed fieldInFormExtensions for template use

In my scenario I would like to pass some validation parameters to my message template (I can store them in $NgModelController) like this:

```html
{{msg | translate: fieldInFormExtensions.$ngModel.validationParams}}
```

In my notify config template I can use already provided field object:
```html
{{ error.message | translate:error.field.$ngModel.validationParams}}
```

validationParams is filled by my custom validators.

It seams that change is pretty safe - just exposing fieldInFormExtensions variable via $scope.
btw. - great library!