pushing before transfering ownership

added new tests and new helper classes
speed improvements
minor fixes

grid/Grid.h

@@ -158,6 +158,12 @@ public:
 		return nodes[hashes[uid]];
 	}
 
+	/** get the center-node the given Point belongs to. or nullptr if not present */
+	const T* getNodePtrFor(const GridPoint& p) {
+		auto it = hashes.find(getUID(p));
+		return (it == hashes.end()) ? (nullptr) : (&nodes[it->second]);
+	}
+
 	/** get the BBox for the given node */
 	GridNodeBBox getBBox(const int idx) const {
 		return getBBox(nodes[idx]);