oc-db: Store version number instead of CN

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.