[ticket/12910] Set get_name_short for Google+ fields

Using get_service name would confuse the ACP dropdowns while fetching the field's type's name, causing it to list 2 "Single text field". Instead specify the template filename instead

[PHPBB3-12910](https://tracker.phpbb.com/browse/PHPBB3-12910)
type_base as it as
````		return 'profilefields.type.' . $this->get_name_short();````
so it'll take care of it