various auto-edits suggested by clang-tidy

GUI/Model/Model/DatafilesTree.cpp

GUI/Model/Model/FitParameterModel.cpp

GUI/Model/Sample/MaterialModel.cpp

GUI/Support/Style/Style.cpp

GUI/View/Canvas/SpecularDataCanvas.cpp

GUI/View/Data/DatafileEditor.h

GUI/View/Info/CautionSign.cpp

GUI/View/Instrument/InstrumentLibraryEditor.cpp

GUI/View/Instrument/InstrumentListing.cpp

GUI/View/Instrument/InstrumentView.cpp

GUI/View/Instrument/InstrumentsTreeModel.cpp

GUI/View/JobControl/JobPropertiesTableModel.cpp

GUI/View/JobControl/JobSelector.cpp

GUI/View/MaterialEditor/MaterialEditorModel.cpp

GUI/View/Plotter/ColorMap.h

GUI/View/Plotter/SpecularPlot.h

GUI/View/Realspace/RealspacePanel.cpp

GUI/View/Sample/SampleListModel.cpp

GUI/View/Scene/MaskGraphicsView.h