Swing tutorials under examples.

Scalified versions of some of the Java Swing tutorials are added to the directory examples/src/main/scala/swing/examples/tutorial.  Hthml and graphics for the demos are placed in examples/src/main/resources/scala/swing/examples/tutorial.  The code has been changed to use the resources in the new layout, provided that the user's classpath points at the 'resources' directory.

All source code has an Oracle copyright.  The main entry points to the examples are stamped with urls for the  Swing tutorial and urls to the original java source codes.
If you use `new MainFrame`, you get the `closeOperation` for free, and I think `open()` as well.