Role Mask Proxy Model

This proxy will act as a mask on top of the source model to intercept data.

An example usage of this proxy is to enable the use of special roles in read-only models. To change the background brush of a QSqlQueryModel for example, you just need to create this proxy, call addMaskedRole(Qt::BackgroundRole) and now you can use setData as the model was writable for that role.