New features for paths

Here are some new features to allow people to find the path to root for any given item as well as to determine if one item contains another. With some tests, even. For #84
After discussion with you and exploration of how HGrid works, no, that request makes no sense, as the root is not an item and so is not part of the path. I have tests that check for trees and leaves that are in the root, and ensuring that they have the proper paths.