Project not found page

[ibilon]

Currently when trying to access a project/version that doesn't exist you get a "Page not found" http://lib.haxe.org/p/doesntExist/ http://lib.haxe.org/p/haxelib_client/4.0.0/ because of https://github.com/HaxeFoundation/haxelib/blob/development/src/website/controller/ProjectController.hx#L44

We need a page for "No such library" "Project foo doesn't have this version".

Customize the 404 page with the actual layout would also be better.