This is a pretty fundamental change in Hugo, but absolutely needed if we should have any hope of getting "multiple outputs" done.
This commit's goal is to say:
* Every file target path is created by `createTargetPath`, i.e. one function for all.
* That function takes every page and site parameter into account, to avoid fragile string parsing to uglify etc. later on.
* The path creation logic has full test coverage.
* All permalinks, paginator URLs etc. are then built on top of that same logic.
Fixes#1252Fixes#2110Closes#2374Fixes#1885Fixes#3102Fixes#3179Fixes#1641Fixes#1989
Note that this looks like overkill for just the logger, and that is correct,
but this will make sense once we start with the template handling etc.
Updates #2701
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
