Draft: Introduce new API for the TGeoTransportSvc

Ben Couturierrequested to merge
dd4hep_ITGeoTransportSvc into master

This commit separates the API for the ITGeoTransportSvc from the DetDesc ITransportSvc. This is needed as the API uses the ILVolume::Interesction class, which uses the DetDesc Material (a pointer to it actually).

Some cleanup of the Service is still to be done.

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