The "Uninstall" button on the module form no longer changes the state of
modules, so that cancelling the wizard will not unexpectedly perform the
uninstallation. The uninstallation is performed only by clicking on the
"Confirm" button on the wizard.
Moreover, the wizard provides clearer information about the impact of the
uninstallation: what apps/modules will be uninstalled and what documents
(models) will be lost.
