WritableProxyModel is a QAbstractProxyModel that allows you to modify the data without modifying the source model.
It is useful for implementing a "dirty" state for a model, where you can modify the data and then commit the changes
to the source model.
Supported features (reimplemented):
- setData
- setItemData
- removeRows
- insertRows
- moveRows (TODO)
- toVariantMap
- to be continued...