[orca-list] Navigate to next smallest/largest object

[Scott Haeger <scott bashautomation com>]

I invite users to try the new navigate to next smallest/largest object.  
The idea behind this feature is that objects that take up more screen 
real estate have more interesting content.  Currently, the key bindings 
are 'o' (go to smaller) and 'shift-o' (go to larger), thus replacing 
navigate to next 'chunk'.  In the future, '+' and '-' may be used and 
navigate to next chunk will be reinstated.  Also of note, switching 
pages (tab browsing) resets the size hierarchy, with the document frame 
being the largest object.  The patch for this feature can be found here 
http://bugzilla.gnome.org/show_bug.cgi?id=447925

Scott