Merge pull request #7 from 4teamwork/pg_org_unit_counters

Extends OGDS Service with the `has_multiple_org_units` method.
Renamed client relationship and define org_units getter and setter instead.
Add a base-class with query helper methods.
Added tests for `AdminUnit.assigned_users`.
Merge pull request #9 from 4teamwork/deif_query_base

Add a base-class with query helper methods.
Added inbox representation to the ogds models.

Every orgunit should has a representation of a inbox.
Merge pull request #10 from 4teamwork/pg_admin_units_org_units

Reworked AdminUnit and Client Relationship.
Merge pull request #8 from 4teamwork/pg_inbox_representation

Added inbox representation
Org-units can prefix their label to another label.
Update company organization form :).