Simplify Window management

Update Compass to re-use the same window when an object is selected, rather than creating a new top-level window. With the current approach I wind up with countless windows on my desktop and have a hard recalling what is what.

Let's re-use the same top-level window and add a "open in new window" context menu item for cases where the user would like to open an additional window (like OS X does with Finder).