* .C ---> .cpp
* removed ../examples from paths
* moved some demo/example files out of doc_tex into their respective place
* now it should build properly, again
which stores the circumcenter.
- Delaunay.dual() now calls the .circumcenter() function of the cell
to retrieve it.
- It implies a new requirement on the TCellBase, for the Delaunay::dual()
case, hence the default model T_cell_base_3 provides a new function
(and the concept is updated).