Refactor deserialization into a callable function (not a part of the dict constructor)
move creation-by-deserialization into MutableNode
move creation-by-crystallization into Node
Add tests for deserialization of dense nodes too.
(minor) remove redundant parameter.
Fix bug in html-closing tag stripper.
Also strip <noinclude> tag.
 Update markup stripping tests to reflect new practice.

 Always nice to see em work - caught the closing tag issue due to the test!