[macOS] finish porting away from eawt

[enh]

there are a few things that still need to be moved over. most notably quit handlers.

note that there's a new API that will let us get rid of the "hidden frame" in Terminator:

https://docs.oracle.com/javase/9/docs/api/java/awt/Desktop.html#setDefaultMenuBar-javax.swing.JMenuBar-

note that the API for setting the dock menu is here now (Java 9+):

https://docs.oracle.com/javase/9/docs/api/java/awt/Taskbar.html

this lets us deal with clicks on the dock icon: https://docs.oracle.com/javase/9/docs/api/java/awt/desktop/AppReopenedListener.html

[enh]

done. dock menu, clicking on the dock, and quit handlers fixed today.

(we can't lose the hidden frame until we require Java 9, and we currently only require Java 8, so i've added a TODO in the code for when we go searching for "what can we clean up now we require Java 9?"...)