Implement next generation modulestore

A new modulestore backed by mongo that changes the data format to
facilitate easy versioning, sharing content between courses, and fast
lookup of course structure and Scope.settings data.

Conflicts:
	cms/djangoapps/contentstore/tests/test_contentstore.py

common/test/data/splitmongo_json/active_versions.json

@@ -0,0 +1,27 @@
+[{"_id" : "GreekHero", 
+  "org" : "testx", 
+  "prettyid" : "test_course", 
+  "versions" : {
+    "draft" : { "$oid" : "1d00000000000000dddd0000" }
+   },
+  "edited_on" : {"$date" : 1364481713238},
+  "edited_by" : "test@edx.org"},
+
+ {"_id" : "wonderful", 
+  "org" : "testx", 
+  "prettyid" : "another_course", 
+  "versions" : {
+    "draft" : { "$oid" : "1d00000000000000dddd2222" },
+    "published" : { "$oid" : "1d00000000000000eeee0000" }
+    },
+  "edited_on" : {"$date" : 1364481313238},
+  "edited_by" : "test@edx.org"},
+  
+ {"_id" : "contender", 
+  "org" : "guestx", 
+  "prettyid" : "test_course", 
+  "versions" : {
+        "draft" : { "$oid" : "1d00000000000000dddd5555" }},
+  "edited_on" : {"$date" : 1364491313238},
+  "edited_by" : "test@guestx.edu"}
+]