Cleanup nproperty::Object

The `nproperty::Object` class contains countless helper methods polluting its namespace. They all should be turned into free-standing friends, just like Qt is doing with the `Q_ENUM()` macro for instance.

Locate the nproperty::Object class and inventory the helper methods currently in its namespace. Read the surrounding metatype and property implementation, then compare the intended free-standing friend approach with the issue’s Q_ENUM reference; done means the helpers are no longer namespace members without changing the experiment’s behavior.

Written by the indexing model from the issue text.