Integrate new file ioslave in KIO job

Summary:
This patch,
1.Adds two new job flags, PrivilegeExecution and NoPrivilegeExecution.
2.Adds code for confirmation dialog to be shown before starting a privilege file operation.
3.Provides slot for privilegeOperationRequested signal emmited by the slave.

Differential Revision: https://phabricator.kde.org/D6832