Modified several drag related methods to return the correct NSDragOperation.  This modification seems to get rid of spuriously invalidated drags that occur  if a previous drag has been cancelled.
Modified several drag related methods to return the correct NSDragOperation. 
This modification seems to get rid of spuriously invalidated drags that occur 
if a previous drag has been cancelled.

git-svn-id: 9ecb4abd5286682cb4be416c220a46cccbbd44e6@3226 7b3f36aa-e6db-49c1-8b4c-66eac1997e64

etoile/EtoileUI,etoile/EtoileUI