To be able to search in this for every kind of operator.
As we cannot do a migration, we have to add a new key to the property
dictionary (@"version_number") which stores the version:
version = exchange_globcnt(CN >> 16)
Instead of the CN structure which is stored in @"version" key.
This way we can do searches for CN to download only missing data from the
given state of the client for this kind of messages.