Fix ripple animation for RTL locales

The animation was invisible because it was going out of screen, also
add a mirrored version of the image to the theme.

https://bugzilla.gnome.org/show_bug.cgi?id=584662

js/ui/panel.js

@@ -706,6 +706,8 @@ HotCorner.prototype = {
                                         x: x,
                                         y: y });
         ripple._opacity =  startOpacity;
+        if (ripple.get_direction() == St.TextDirection.RTL)
+            ripple.set_anchor_point_from_gravity(Clutter.Gravity.NORTH_EAST);
         Tweener.addTween(ripple, { _opacity: finalOpacity,
                                    scale_x: finalScale,
                                    scale_y: finalScale,