Use default keyword for default ctors.

Applications/DataExplorer/Base/OGSError.cpp

...ations/DataExplorer/Base/QNonScalableGraphicsTextItem.cpp

Applications/DataExplorer/DataView/ColorTableModel.cpp

...ions/DataExplorer/DataView/DataExplorerSettingsDialog.cpp

...ations/DataExplorer/DataView/DiagramView/DetailWindow.cpp

...cations/DataExplorer/DataView/DiagramView/DiagramList.cpp

Applications/DataExplorer/DataView/DiagramView/QArrow.cpp

...tions/DataExplorer/DataView/DiagramView/QGraphicsGrid.cpp

...ications/DataExplorer/DataView/DirectConditionGenerator.h

Applications/DataExplorer/DataView/ElementTreeModel.cpp

...ications/DataExplorer/DataView/GeoOnMeshMappingDialog.cpp

Applications/DataExplorer/DataView/GeoTreeItem.h

Applications/DataExplorer/DataView/GeoTreeModel.cpp

Applications/DataExplorer/DataView/LicenseDialog.h

Applications/DataExplorer/DataView/LinearEditDialog.cpp

Applications/DataExplorer/DataView/MeshAnalysisDialog.cpp

...ations/DataExplorer/DataView/MeshElementRemovalDialog.cpp

Applications/DataExplorer/DataView/MeshLayerEditDialog.cpp

...ions/DataExplorer/DataView/MeshQualitySelectionDialog.cpp

Applications/DataExplorer/DataView/MeshValueEditDialog.cpp