Added support for articy metadata in the UPARAM specifier

[jeremyabel]

This allows you to restrict classes via function parameters:

UFUNCTION(BlueprintCallable)
void AddQuest(UPARAM(Meta = (ArticyClassRestriction = MyQuestEntity)) FArticyId Quest);

This works the same way as the FArticyId details widget. ArticyExactClass also functions as expected. Should I add this for FArticyRefs as well?