Replacing the glui GUI with a Qt5 GUI

3DTK provides a program to visualize point clouds called “show”. GUI of “show” is written by glui framework now, but glui framework is old and difficult to maintain. Therefore, it is necessary to replace “show” GUI with a more general framework such as Qt5. 3DTK developers have already started this rewriting, and this project is called “qtshow”. However, “qtshow” still misses a lot of functionality compared to “show”. Because of this, I improve these problems and add some features which are in “show” but not in “qtshow”.