core: Continue PieCrust3 refactor, simplify pages. The asset pipeline is still the only function pipeline at this point. * No more `QualifiedPage`, and several other pieces of code deleted. * Data providers are simpler and more focused. For instance, the page iterator doesn't try to support other types of items. * Route parameters are proper known source metadata to remove the confusion between the two. * Make the baker and pipeline more correctly manage records and record histories. * Add support for record collapsing and deleting stale outputs in the asset pipeline.

--- a/piecrust/sources/autoconfig.py	Wed May 17 00:11:48 2017 -0700
+++ b/piecrust/sources/autoconfig.py	Sun May 21 00:06:59 2017 -0700
@@ -15,7 +15,9 @@
         settings to their generated pages based on those pages' paths.
     """
     def __init__(self, app, name, config):
-        DefaultContentSource.__init__(app, name, config)
+        super().__init__(app, name, config)
+
+        config.setdefault('data_type', 'page_iterator')
 
         self.capture_mode = config.get('capture_mode', 'path')
         if self.capture_mode not in ['path', 'dirname', 'filename']: