Add the first edje examples about the usage of EXTERNAL parts.

Add the first edje examples about the usage of EXTERNAL parts.
This example show 5 buttons that you can click to perform some
simple actions, like changing the label or the icon of the buttons.

The example also spot a bug: external buttons with label AND icon
have layout issue. Standard icons are not visible at all while custom
icons don't get the size calculated correctly.
Buttons with only the icon work well instead.
Can someone look at this?

Thanks
DaveMDS

git-svn-id: http://svn.enlightenment.org/svn/e/trunk/edje@53182 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33