Warning! this commit introduces a strict face definition to prevent ugly bugs in modules.

The rule is that start node != end node this is now checked when inserting the data. If someone wants to insert an element where start node == end node the last node is removed.
removed centroids from  tbvectordata.  Since the calculation of centroids had huge problems when using big numbers which happens in GIS all the time. The methods are now in CGALGeometry which use cgal as a backend and the get it right!
moved unit tests