Ensure tab titles are correct for script window. Refs #5006

Code/Mantid/MantidPlot/src/ScriptFileInterpreter.cpp

Code/Mantid/MantidPlot/src/ScriptFileInterpreter.h

Code/Mantid/MantidPlot/src/ScriptManagerWidget.cpp

Code/Mantid/MantidPlot/src/ScriptManagerWidget.h

Code/Mantid/MantidPlot/src/ScriptingWindow.cpp

...Qt/MantidWidgets/inc/MantidQtMantidWidgets/ScriptEditor.h

Code/Mantid/MantidQt/MantidWidgets/src/ScriptEditor.cpp