OptimizerG2O::saveGraph() should use a ParametersMap when exporting or should not be static (OptimizerG2O would be initialized with a ParametersMap).

In the MainWindow, when exporting the poses, the parameters in Preferences are not used. Same thing for DatabaseViewer, the parameters in the database are not used. Because of that, we cannot choose if we want to export with vertigo edges or not for g2o format.