Fixed #7596. Added Model.objects.bulk_create, and make use of it in several places. This provides a performance benefit when inserting multiple objects. THanks to Russ for the review, and Simon Meers for the MySQl implementation.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16739 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -8,9 +8,10 @@ all about the internals of models in order to get the information it needs.
 """
 
 import copy
-from django.utils.tree import Node
+
 from django.utils.datastructures import SortedDict
 from django.utils.encoding import force_unicode
+from django.utils.tree import Node
 from django.db import connections, DEFAULT_DB_ALIAS
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist