`UEditorSubsystem` Doesn't override its virtual methods
With this code, `USLEditorSubsystem` `initialize()` method is not being called.

```nim
include nuegame
import editorsubsystem

uClass USLEditorSubsystem of UEditorSubsystem:
    (BlueprintType)

    # DOESN'T WORK (But the subsystem is created and can be viewed in the Editor)
    proc initialize(collection : var FSubsystemCollectionBase) {.virtual, override.} =
        self.printString("USLEditorSubsystem INITIALIZED")

uClass USLEngineSubsystem of UEngineSubsystem:
    (BlueprintType)

    # WORKS
    proc initialize(collection : var FSubsystemCollectionBase) {.virtual, override.} =
        self.printString("USLEngineSubsystem INITIALIZED")
```