README updated

README.md

@@ -74,3 +74,6 @@ implemented:
   fast access to the smallest and largest entity.
 - Provide Interpolation / hierarchic Geometry-Objects, like the geometryInFather
   for father-child relations.
+- Entities could be wrapped-up to provide a relation to the grid (-index) it
+  belongs to.
+- Maybe provide Intersections between hierarchic entities