Window attention blinking rate option.
Signals: disconnect within try catch.
Fix warnings: destroy SlicerActor's actor in the parent's destroy() instead of the child's destroy().
Fix warnings: check if style is empty, and set style null instead of ''.
Fix warnings: Gnome-Shell's global.get_current_time() returns 0 sometimes.
Check whether a window requires attention after trackerWindow has been created.
Added move method.
Changed deprecated add_actor and remove_actor where possible.
Minor fixes: check if this._childrenObjects is non-zero, add D('<') when preferences widget is built.
Keep windows/apps in oldest-newest order even if extension is restarted.
Gnome-Shell 3.9: take care of affectsInputRegion.