Add a new signal content_object_init

It's sent when a new content object is created: Page, Article

pelican/contents.py

@@ -11,7 +11,7 @@ from sys import platform, stdin
 
 from pelican.settings import _DEFAULT_CONFIG
 from pelican.utils import slugify, truncate_html_words
-
+from pelican import signals
 
 logger = logging.getLogger(__name__)
 
@@ -106,6 +106,8 @@ class Page(object):
         if 'summary' in metadata:
             self._summary = metadata['summary']
 
+        signals.content_object_init.send(self.__class__, instance=self)
+
     def check_properties(self):
         """test that each mandatory property is set."""
         for prop in self.mandatory_properties: