DatabaseHandle :: LoadExtensions - Refresh extension property definitions

When changing the database extension schema from within an application or when changing the database or dictionary extension schema by another application, the function may be called in order to reload the updated extension schema. The function only adds new extension property definitions without changing or updating definitions that have been loaded before. In order to completely reload the extension schemata, the application has to reopen the database in order to ensure, that extension definitions are not in use anymore.