Update to new emblem names

[Luca Ferretti <elle uca libero it>]

There are some open bugs from me about emblem icons.

The main issue is: gnome-icon-theme is quickly moving to named icons
defined in Icon Naming Spec while Nautilus is still using old ones.

Besides, old named icons will be one day deprecated (from
gnome-icon-theme) and should be moved in another place.

By now, could someone take care of following bugs?

http://bugs.gnome.org/451510 - emblem-nowrite icon is legacy, use
emblem-
http://bugs-gnome.org/451508 - emblem-noread icon is legacy, use
emblem-unreadable

http://bugs.gnome.org/451507 - emblem-desktop is legacy