serve: Refactoring and fixes to be able to serve taxonomy pages. * Page sources' `findPagePath` is renamed to `findPageFactory`, so that it also returns source metadata. * Page refs now store possible hits more properly, and use the previous point to also store metadata. As a result, they can also return a proper factory. * Implement `findPageFactory` correctly in all built-in sources. * When the Chef server matches a taxonomy page, get the source metadata from the page ref in order to make a more proper page. * Make the `getRoute(s)` functions explicitely say if they want taxonomy routes or not.

--- a/piecrust/page.py	Sun Apr 26 08:34:27 2015 -0700
+++ b/piecrust/page.py	Sun Apr 26 15:07:40 2015 -0700
@@ -57,7 +57,8 @@
 
     @cached_property
     def path(self):
-        return self.source.resolveRef(self.rel_path)
+        path, _ = self.source.resolveRef(self.rel_path)
+        return path
 
     @cached_property
     def path_mtime(self):