Clear tk geom

The initial objective of this PR was to remove all dependencies from DDD from the objects used in Reco
and, at the same time, reduce the memory footprint of the tracker geometry itself.
Unfortunately the two objectives could not be fully achieved because of the implementation of Alignment.
My personal conclusion is that it will be very difficult to optimize the access to geometry information w/o a major reimplementation effort of the Alignment infrastructure. Given the current lack of person-power in that area I do not see how it can ever happen.