The new logic for creating Page objects from old node types
didn't include itself in the translation logic, so
`IsTranslated` returned falsely false for sites with only two languages.
The `AllTranslations` method also returned too few pages in that case.
This commit fixes that.
Fixes#2812
This includes removing the error return value from Permalink and RelPermalink.
We ignore that error all over the place, so we might as well remove it.
Updates #2297
