Automatically generate QML enum documentation from C++

If we expose a function accepting or returning an enumeration from C++ to QML, the documentation lists the type simply as "enumeration".

However, if the enum is already documented in C++, and the containing class or namespace is registered to QML, we should be able to do better: Namely, we can reuse the existing documentation to extract the enumerator (and value) description. The only thing that would need to change is replacing NameSpace::Enumerator with RegisteredName.Enumerator.

That would avoid manual repetition of documentation, which is prone to become stale.

From a user's point of view, it would be ideal if this could be fully automated; it would however be a vast improvement if we could do something akin to

\generateQmlEnumDoc