Reintroduce immutable property
For compatibility, reintroduce a Q_PROPERTY called immutable which is true whether the immutability is not mutable.
This makes it compatible with the existing QML, for which it's a clearer API to be just a bool. If needed for more granularity between UserImmutable and SystemImmutable, a new property can be added later, but it's still better to have a simpler bool by default.
Edited by Nate Graham