widget-factory: add desktop file for widget factory
demo: add icon
demo: Add desktop file
demo: use the installed named icon
widget-factory: add icon
widget-factory: use new icon instead of gtk logo
Updated POTFILES.skip
Use a big icon in the stack example

We used a 256x256 before. Keep doing that.
widget-factory: Make the About dialog actually transient

It's an app action, not a window action.
widget-factory: Update copyright in about dialog