preliminary hack fix for synthetic reference issue

preliminary hack fix for synthetic reference issue

           RecentlyOpened
         inner/ /subclasses
       JalviewFileChooser
          \          /
           JFileChooser
                 Component

So Component can be retrieved two ways through JFileChooser. (1) as the
original JalviewFileChooser object
(2) as the superclass of RecentlyOpened.

I will look into it. For now it is sufficient to simply move
RecentlyOpened to be at least a static class. I just made it another
top-level class.