The prepares for next-server.
I also took this as an opportunity to get all build directory paths from a single location, as they were previously scattered across webpack/babel plugins and loaders.
* Initial implementation of next export without exportPathMap
* Shorter message
* Set up flow
* Create pages manifest
* Use pagesManifest for next export
* Fix tests
* Document defaultPathMap
* Replacing the path is no longer needed
* Use posix normalize for consistent behaviour
* Remove second instance of examples
* Add comment about what pages-manifest does
* Make windows path a route