Implemented a new proxy model to transpose the source model.
Rows will become columns and vice-versa.
Both flat and tree models supported.
[ChangeLog][QtCore] New class QTransposeProxyModel to
swap rows and columns of the source model.
Change-Id: I902963c6b81aa0f63b5ad2bddca538f28b565084
Reviewed-by: David Faure <david.faure@kdab.com>
