code: static <P extends GISPrimitive, N extends AbstractGISTreeSetNode<P, N>>
  		boolean addInside(AbstractGISTreeSet<P, N> tree,
  			N insertionNode,
  			P element,
  			GISTreeSetNodeFactory<P, N> builder) {
  		return addInside(tree, insertionNode, element, builder, true);
  	}
docs: Add the given element inside the given node (or one of its children).
  
  @param <P> is the type of the primitives.
  @param <N> is the type of the nodes.
  @param tree is the tree to update.
  @param insertionNode the receiving node.
  @param element the element to insert.
  @param builder is the node factory.
  @return success state.