New grid layout behaviour for workspace switching

[Alexandre Kaspar <alexandre kaspar epfl ch>]

Hi everybody,

I found how to change the workspace-switching behaviour so that now I
can switch also in a vertical manner (with <Ctrl><Alt> Up / Down), and
the workspace transition looks fine.
The workspaceSwitcherPopup is here better because the grid doesn't go
out of the screen as the flat horizontal row does (on my 1376 pixels
wide screen, it does so for big grids - more than 7 workspaces).

You can get my file changes on :
http://www.wox-xion.ch/2010/04/16/gnomeshell-new-grid-layout/

There are two three new images (two rotations and a cross) to complete
the workspaceSwitcherPopup interface for other cases, as well as other
minor changes.
The <Ctrl><Alt><Shift> Up / Down shortcut doesn't work as of now because
I didn't find where it was managed. (this also means that the
<Ctrl><Alt><Shift> Left / Right shortcut doesn't follow my new grid
layout behaviour... which is sad and incoherent, but I couldn't get a
better solution for now). My new layout behaviour is working (except for
the window-switch. And it still uses the special (strange, but finally
normal) order of workspace creation and deletion.
My solution to locates things is a 4x4 only solution. It would be better
to solve the general solution (and maybe not hard), but since I only
wanted to get it working for now, I didn't do anything which was useless
at that time.

If you thing it is worth being integrated in GnomeShell, then I may add
an entry in bugzilla.

Have a nice week
Alexandre Kaspar