Provide the easy to use interfaces for selection of the elements from BVH tree.
The selection rules should be implemented in the selector class derived from *BVH_Traverse* or in *BVH_PairTraverse* in Reject/Accept methods.
The *BVH_Traverse* is used for selection of the elements from the tree.
The *BVH_PairTraverse* is used for selection of the pairs of elements from two BVH trees.
Auxiliary changes:
- Two methods BVH_Box::IsOut(OtherBox) and BVH_Box::IsOut(Point) have been added;
- Added methods for conversion of Bnd boxes to BVH boxes
Added new class *BVH_Tools* containing useful static methods operating on BVH points and boxes.
The classes BRepExtrema_OverlapTool and BVH_DistanceField have been rebased to use the new traverse methods.
