Move serializeNode to DOMUtils and use it for data-mw too

* Smaller data-mw with adaptive quoting.
* Updated parserTests with new output
* Also add a serializeChildren method that works similar to innerHTML.
* Move HTML normalization to DOMUtils to avoid cyclic dependencies
* Disable non-IE WS to space normalization pass, needs to be improved. See bug
  55588. This leads to some new passes and some new fails.

Change-Id: I392881bd8a0cfd9f116e70e9a52d1ef14bbd568b