Incomplete d'n'd support for location bar icon

[Luca Ferretti <elle uca libero it>]

Now (HEAD branch) you can use the location bar icon to do d'n'd
operations on open folders. This is great.

But it seems that the only target for d'n'd operations starting form
location bar icons are Desktop and Nautilus folder icons and windows. 

For example you can't drop it on gnome-terminal windows or in the
GtkFileChooserButton on Search tool. And please note that those items
are allowed targets when you start your d'n'd operation from folder
icons.

Christian, could you finish it?

BTW could someone "explore" Nautilus d'n'd behavior? Is it complete as
well as Mac Finder?

-- 
Luca Ferretti <elle uca libero it>