Bug fix: need to set the state machine node before deciding whether we
need children.
Fixing warnings found.
Response to more warnings.

XmlSchemaDocumentNodes are never reused; removing that functionality.
Also removing the pool of tree nodes backing it.
Adding test document with only the root element.

Bug fix: Paths that go through earlier sequence elements are preferred
over paths that go through later sequence elements.  This is now more
important than path length.
Finished first test.

When leaving the root, have one more path representing the parent walk
into nothingness.
Tests don't pass yet, but committing here.

We need to keep track of where we are in the children.  This way when we
don't need to backtrack our steps when we start a new element under an
existing one.

Next up: every time we increase the number of occurrences, we need a new
instance of that node in the tree.
Adding a SIBLING concept for when we create new occurrences of the same
tag.
A document node can have multiple occurrences, and likewise needs
multiple sets of children.  Adding this functionality.
Automatically create new children when the number of iterations
increase.
Function to check if all of the requirements of the current
XmlSchemaDocumentNode have been fulfilled.