Implement file->closeModel operation in DuSE-MT

Change-Id: Icd4bd36725c9d8c9b8e4580fd831356199087675
Reviewed-by: Sandro S. Andrade <sandroandrade@kde.org>
Add major improvements in DuSE-MT basic workflow

Change-Id: Ib2da2cd01e98e4e3ed6d51057228e2dae854cb60
Reviewed-by: Sandro S. Andrade <sandroandrade@kde.org>