move CHANGELOG, CREDITS and LICENCE to the top-level directory

remove OrientedBoundary and Unique2: Boundary now always returns the signed (oriented) boundary: this is what we used to do in 
the old Geo. To get valid entity numbers, just use Abs()

* modified new internal CAD APIs to always preserve the order of the entities in transformations (even across dimensions)
* refactored extrusions - the refactoring of the old Geo code is complete (the parser does not include Geo.h anymore!)
* fixed incoherence when deleting internal entities during boolean operations, after synchronzing them with GModel
* made sure we don't bind OCC entities to multiple tags

"Ruled Surface" makes no sense: use "Surface" instead. A "Surface" will try to do the filling "the best it can".

No commit message

No commit message

No commit message

No commit message