Fixed #1142 -- Added multiple database support.

This monster of a patch is the result of Alex Gaynor's 2009 Google Summer of Code project.
Congratulations to Alex for a job well done.

Big thanks also go to:
 * Justin Bronn for keeping GIS in line with the changes,
 * Karen Tracey and Jani Tiainen for their help testing Oracle support
 * Brett Hoerner, Jon Loyens, and Craig Kimmerer for their feedback.
 * Malcolm Treddinick for his guidance during the GSoC submission process.
 * Simon Willison for driving the original design process
 * Cal Henderson for complaining about ponies he wanted.

... and everyone else too numerous to mention that helped to bring this feature into fruition.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11952 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/multiple_database/fixtures/multidb.default.json

@@ -0,0 +1,26 @@
+[
+    {
+        "pk": 1,
+        "model": "multiple_database.person",
+        "fields": {
+            "name": "Marty Alchin"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "multiple_database.person",
+        "fields": {
+            "name": "George Vilches"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "multiple_database.book",
+        "fields": {
+            "title": "Pro Django",
+            "published": "2008-12-16",
+            "authors": [["Marty Alchin"]],
+            "editor": ["George Vilches"]
+        }
+    }
+]