Add language pairs attribute to users

[cfedermann]

Add an additional "language pairs" attribute to user profiles.

This does require the addition of customised user profiles; see the Django documentation over here:

• https://docs.djangoproject.com/en/1.3/topics/auth/#storing-additional-information-about-users

Seems this has improved greatly in Django v1.5:

• https://docs.djangoproject.com/en/1.5/releases/1.5/#configurable-user-model

[cfedermann]

Solved using auth.Group instances. Works nicely!