Fix a bug involving the Vulcan Death Grip closing the wrong app

If you have expander turned on with expanded apps and you quickly remove teams with the VDG
you can remove a team not under your mouse pointer, instead you remote the team above. This
is because the window watcher thread hasn't updated yet so the TeamItemAtPoint() method
reads a window menu item instead of the team item. The solution is to lock the window
watcher thread and explicitly remove the window menu items in RemoveTeam().

This bug can be really bad if you accidentially VDG Tracker as your system gets hosed until
you restart Tracker or reboot.
Update expander arrows to point right or down (if expanded)

... like BeOS R5. I looked in the commmit logs for this one and there wasn't really any
explination for why this got changed, so, I'm changing it back to the way it was in R5 which
is right arrow for unexpanded, down arrow for expanded. Please yell at me if this change
was intentional.