@WIP: Add prefix field to a profile node type.

#5744 

WIP

As mentioned in the issue above, a field named "prefix" is added to a profile.
Node form for a profile:
![selection_239](https://cloud.githubusercontent.com/assets/4497748/3214155/adb34964-efa8-11e3-889b-89768e3cdd90.png)

The ``john/people`` page:
![selection_238](https://cloud.githubusercontent.com/assets/4497748/3214157/b2c4f600-efa8-11e3-8463-c5e2104da2e4.png)