SIRS Knowledge Source [new translator]

New translator for SIRS Knowledge Source, a ProQuest K-12 database
(Note: this only covers Knowledge Source, not SIRS Discoverer or SIRS Decades)
pretty sure that, unless `root` is a self-closing node, this can never fail. It would always be able to select the white-space nodes surrounding elements. This makes the `if` statement below unreachable code, but it also makes me wonder if this is what you actually want.