In Realm Java, we have a concept called RealmConfiguration.initialData() which is a way to populate a Realm file the first time it is opened. This is pretty helpful in a lot of scenarios and should be added to Kotlin as well.

It isn't supported in ObjectStore however, so should be added there, and the current behavior of resetting the Realm file will also cause problems with such a block. See #301

Proposed API
```
val config = RealmConfiguration.Builder(schema = setOf(...))
.initialData

.build()