Call profile fields controller with correct args

My intension:
I wanted to make the profile fields on the user page persisted.
The fields 
* About
* Study
* Organization
* Bank account

My changes:
1. In the HAML, the profile fields controller is called with the profileable type.
2. In the controller, if the profileable type is missing, an exception is raised.
3. In the controller, the profileable is loaded before the authorization and only for create

The effect:
1. New fields are still visible after a reload of the user page.
2. Fields can be deleted.