Right now RealmObject.version is an extension method, but the plan was to move it to an interface method. This has a number of complications though:

• version is a very generic name and there is a high chance it conflict with user code
• If we change it to e.g. realmVersion, should we also change Realm.version, RealmResults.version and RealmList.version ?
• Exposing it as RealmObject.realm.version also seems problematic as we don't have multiple Realm instances.

This PR is about evaluating what the best way of doing it is? variable or function? And what the final name should be.