WIP - Extract namespaces from xpaths to utility functions

I extracted same functions and infix operators on ``XmlNode`` type to ``Xml`` module - feedback welcome.
Also, plan to spread this even more, that is ``ProjectFile`` and elsewhere where we parse xml.

Note: I haven't tested the ``followODataLink`` function after refactor
yes that true, but custom operators make it much harder for noobs to read the code.
We should stick to |> and maybe >> in special case.