Serialization in V2

We should consider how we should align XProc new serialize function [1] in
XPath 3.0 should and their XML syntax for serialization options [2].

We may also need to update our serialization options, etc. against the
common specification [3] or some newer version of it.

[1] http://www.w3.org/TR/xpath-functions-30/#func-serialize
[2]
http://www.w3.org/TR/xslt-xquery-serialization-30/#serparams-in-xdm-instance
[3] http://www.w3.org/TR/xslt-xquery-serialization/

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics