Hook Particle to the other systems

Had to manually merge a change set for this

util/tree.c

@@ -174,3 +174,13 @@ tree_Node *tree_Node_Previous(tree_Node *node) {
 		return result->father;
 	}
 }
+
+
+size_t tree_Count(tree_Tree *tree) {
+	size_t cnt = 0;
+	for (tree_Node *i = tree_FirstNode(tree);
+		 i != NULL;
+		 i = tree_Node_Next(i))
+		cnt++;
+	return cnt;
+}

util/tree.h

@@ -69,6 +69,9 @@ tree_Node *tree_Node_Next(tree_Node *node);
 // Node_Previous returns the previous node. Returns NULL if first.
 tree_Node *tree_Node_Previous(tree_Node *node);
 
+// Count walks the tree and counts how many nodes are there in the tree.
+size_t tree_Count(tree_Tree *tree);
+
 
 #ifdef __cplusplus
 }