Fix opengever task tests.
Fixed OrgUnit Builder: allways create groups when assign users.
TaskBuilder: Add default values for required fields.

The SQL representation in `opengever.globalindex` defines no db-constraints
for the required fields, so it makes sense to define default values for
those fields.
Response and DocumentsTransporter: change behavior from remote-client
to remote-admin_unit.
Changed oguid composition: use admin_unit_id instead of the client_id.
Task overview: use admin_unit_id instead of the client_id.

Because of the task rework the ogduid and mandanten behavior has changed.
It's now the admin_unit who decide if a task is remote or not.
Fixed task css helper.
Diverse tests fixes: because of the task rebuild.
Change behavior of remote task requests and views.

Because the task model has changed,
it compares now the current_admin_unit's instead of the client ids.
pyflakes.
Merge pull request #272 from 4teamwork/migrate-task-columns

Migrate task columns
Use and configure new query base from `opengever.ogds.models`.

See https://github.com/4teamwork/opengever.ogds.models/pull/9.
Dropped no longer used contact_information utility query.
AdminUnit builder: assign org_unit to admin unit when wrapping a orgunit.
Fixed AdminUnitBuilder: dropped doubled `after_create` method.
Introduce a specific query class for the Task sql-representation.

The query class should replace the ITaskQuery utility in the feature.
PersonalOverview: Rework tasklistings, so that all view queries the Globalindex.
GlobalIndex Syncer: convert sequence_number to a str for the sql-representation.

Right now the Sequencenumber is a String field in the task model,
therefore we have to be sure that the `sequence_number` and the
`dossier_sequence_number` are converted to a string.

The DB model should be ajusted and migrated in the feature.
Merge pull request #283 from 4teamwork/pg_task_tabs_rework

Rework personaloverview tasklistings
WIP: fix opengever task tests.