W2：GUI

【参考】

GUI配置 http://www.tutorialspoint.com/python/python_gui_programming.htm

样板 http://www.cnblogs.com/kaituorensheng/p/3287652.html

教程 http://effbot.org/tkinterbook/tkinter-hello-again.htm

官方教程 https://docs.python.org/2.7/library/tkinter.html

图像目录 http://infohost.nmt.edu/tcc/help/pubs/tkinter/web/cursors.html

QGIS GUI GUI http://www.th7.cn/Program/Python/201508/536247.shtml 【问题】 label is not defined