option to read and display vtk files(#33)

forms/mainwindow.ui

src/MainWindow.cpp

src/MainWindow.h

src/SaxParser.cpp

src/SaxParser.h

src/SystemSettings.cpp

src/SystemSettings.h

src/ThreadVisualisation.cpp

src/ThreadVisualisation.h

src/geometry/FacilityGeometry.cpp

src/geometry/FacilityGeometry.h

src/geometry/GeometryFactory.cpp

src/geometry/GeometryFactory.h

src/geometry/LinePlotter2D.cpp