Merge pull request #1 from ickard/master

Please pull it ;)
Added server code. Fixed date handling in client C++, it no longer sends it to the server or put it in the serialized json. Added picojson header.
prendo C++ client code was never removed from old location in previous commit.
Fixed a typo in cronjob.py.
Fixed an include order bug in prendo.h.
Updated to support the old Master/Slave data store. The new High Replication
data store works unreliably, see
http://stackoverflow.com/questions/11063597/read-delay-in-app-engine-datastore-after-put.
Revert "Updated to support the old Master/Slave data store. The new High Replication"

This reverts commit 6762952e58e94c81b8d3a7ff27554183a06c6040.
Add support for the High Replication data store

Use ancestor queries and a common singleton entity for all Score
instances to avoid consistency issues with the High Replication data
store.

See
https://developers.google.com/appengine/docs/python/datastore/structurin
g_for_strong_consistency for more info