Fixed transporting task with the OGDS Transporter between different admin_units.

The commits 9b75a9d and 910c829 brakes transporting tasks with the
`opengever.ogds.base.transporter.Transporter` from one admin unit to another.

I've added an tests for transporting tasks and refactored the `Transporter` object creation completely.
Dropped no longer used interface `ogds.base.interfaces.IObjectCreator`.
Dropped the ITransporter utility and replace it with a simple object.
Merge pull request #693 from 4teamwork/pg_ogds_transporter_fix

Fixed transporting task with the OGDS Transporter between different admin_units.