OGDSService inclusion

This PR is the counterpart of these changes https://github.com/4teamwork/opengever.ogds.models/pull/5.

We replaced some methods from the `IContactInformation` and replaced it with the use of the new  `OGDSService` and the extended [User Class](https://github.com/4teamwork/opengever.ogds.models/blob/pg_user_model_extraction/opengever/ogds/models/user.py#L49) 

The changes in the IContactInformation are not exhaustive, there is still a lot to drop, refactor and move in to the `OGDSService`. But we go step for step.

@lukasgraf could you take a look?