New design work started

[Alexander Larsson <alexl redhat com>]

I've started implementing the new design mockups in the new-design
branch. Its very early stage, and most things don't work. In case you
want to follow it its there to look at at least.

Also, i implemented some lowlevel support for transparent windows in gdk
that we can use to get shadow from the notification overlay like in the
mockups. This is in latest gtk+ git.