replace Manhattan::ProgressBar by QProgressBar

This fixes the issue 2503 (GUI: Material editor is a semi-modal toplevel window instead of modal dialog)

http://apps.jcns.fz-juelich.de/redmine/issues/2503

replace Manhattan::MiniSplitter by QSplitter

GUIHelpers::Error::what() returned a char* to a temporary QByteArray which is invalid after leaving what()

The crash happens because of trying to create subdir "autosave" in the project directory, which is not existing anymore.

The fix
a) avoids creating the subdir, if the project dir is not existing
b) catches any exception in autosave, so autosave itself never causes a crash by an unhandled exception

transparent