Add childSelector/childSelectorAll helpers.

Also update to latest (unreleased) domino in order to get a working
implementation of Element.matches() and to fix the [lang] and [dir]
selectors.

Change-Id: I7a17c5d5ed5afdf4f035cee4fa43357d257a8801
Basic table support.

Doesn't handle COLSPAN or ROWSPAN attributes yet; doesn't handle tables
longer than a single page; doesn't handle cell alignment.

Change-Id: I6d5a0120731409cd86ad17a27b9eaa58849da7f6