Dot-Notation for "_id"

Note: Migrations can't use "Dot Notation"!

Migrations run on pymongo, not mongokit.
So they can't use the "Dot Notation".
This isn't really a big issue, as migrations are anyway
quite mongo specific.

mediagoblin/tools/pagination.py

@@ -53,7 +53,7 @@ class Pagination(object):
             cursor = copy.copy(self.cursor)
 
             for (doc, increment) in izip(cursor, count(0)):
-                if doc['_id'] == jump_to_id:
+                if doc._id == jump_to_id:
                     self.page = 1 + int(floor(increment / self.per_page))
 
                     self.active_id = jump_to_id