Description of Problem:

Sometimes, you forget that you have already opened
your HOME folder in Nautilus. If you dble-click on
the nautilus' icon, it brings up a second HOME window.

Here's my idea to prevent that:

If you try to open a new window of Nautilus on a
specified folder, Nautilus should open this window
only if:
 - there is no other Nautilus window pointing to
this folder
 - or there is exactly one Nautilus window
pointing to this folder and this windows hasthe focus
 - or there is more than one Nautilus windows
pointing to this folder (visible or not)

If there is exactly one Nautilus window pointing
to the same folder BUT this window isn't focused,
Nautilus should bring this window to the front
(bringing it to the user's current wworkspace if
needed) and focus it.

That way, if someone really wants to open 2
Nautilus windows, it's still possible but Nautilus
will sort of warn you that you already have opened
this windows by bringing it to the front.