Add the XSLT execution engine: template matching against the source tree
(highest priority, then last declared, with the built-in rules), the
apply-templates processing model, and instantiation of the sequence
constructor. Implements apply-templates with sort, value-of, for-each, if,
choose, element, attribute, copy, copy-of, call-template, variable, literal
result elements, and attribute value templates, over the XPath engine. The
identity transform round-trips a document including attributes. Collapse the
completed Transformation roadmap block into the shipped summaries.
Closes#15Closes#16Closes#17Closes#18Closes#3