Wrap pymongo connections in MongoProxy.

PLAT-71
Added autoretry_read decorator to methods which use mongo cursor.

PLAT-71
Wrapped Split MongoConnection in MongoProxy.

PLAT-71
Merge pull request #5816 from edx/usman/plat71-mongo-autoreconnect-errors-2

Proxy to retry on mongo Autoreconnect errors.
Update translations (autogenerated message)
Merge pull request #5897 from edx/sarina/20141110-update-translations

Update translations (autogenerated message)
Consistently name edX branded elements within the LMS [OPEN-300]
Translate "Powered by Open edX" string