Reintroduce Wanda The Fish

When transitioning from gnome-panel to gnome-shell in 3.0 we
lost the ability to summon the wisdom of the mythical fish.
This patch restores this, for the few adepts that are aware of
the magical incantation.
(Not as configurable as the original one, but it's an easter egg
after all...)

https://bugzilla.gnome.org/show_bug.cgi?id=666606