Opentaskreport: Use `Actor.lookup` instead of `ContactInfo.describe`.
Fix me: Fixed UserActor, the label function hasn't worked.
LaTex tasklistings: reworked tasklistings.

Some of the changes are only temporary and will be removed after implementing
the issue https://github.com/4teamwork/opengever.core/issues/289.
DossierContainer: Added `responsible_label` property.
Droped no longer used `IContactInformation.list_inboxes`.
Reworked ListGroupMembers view, use the ogds_service and Actor class.

Test is missing for the ListGroupMembers view.
DocumentOverview: use Actor.get_link instead of `IContactInformation.render_link`.
CheckedOutViewlet: use Actor.get_link instead of `IContactInformation.render_link`.

Added tests for the viewlet.
DossierByline: use Actor.get_link instead of `IContactInformation.render_link`.
reworked `linked_ogds_author` helper use Actor.lookup.

Using Actor.get_link instead of `IContactInformation.render_link`.
Reworked user link geneartion, use Actor.lookup.

Use Actor.get_link instead of `IContactInformation.render_link`.
Task Overview: use Actor.get_link instead of `IContactInformation.render_link`.
Droped no longer used `IContactInformation.render_link`.

The link geneartion is now handeld with Actor lookup's.
Rework ogds vocabularies: use Actor.lookup instead of `IContactInformation.describe`
Rework Actor lookup: create object in lookup method.
Cleanup.
Merge pull request #291 from 4teamwork/deif-drop-describe

Rework label generation for all actors.
Reworked ogds tabbedview helpers.

* Helpers: Use actor lookup instead of `IContactInformation.describe`.
* Use helper only in tabbedview und LaTex listings, appart from that
use direct actor lookup.
Merge pull request #293 from 4teamwork/pg_tabbedview_helpers_rework

Tabbedview helpers rework
Task SearchableTextExtender: use Actor lookup instead of IContactInformation.describe.