Right-click palette reveal doesn't work well in the Frame

[Eben]

Right-clicking on an object should immediately reveal that objects secondary palette, akin to standard context menus. A recent patch added this functionality (http://dev.laptop.org/git?p=sugar-toolkit;a=commit;h=976abfc0b72cf29edfedf7b3cbd51a4b82916c54).

While this works fine in activity toolbars (at least, those I've tested) and the places (top) edge of the Frame, it does not work for the clipboard, people, or devices edges at all. This is a basic interaction principle that we want to reinforce, so it's critical that it behaves as expected everywhere in the system.