Changed file chooser parent to: this instead of this.window

In GNOME Shell 3.12, using this.window as the parent gave this error:
JS ERROR: TypeError: Object is of type GdkX11Window - cannot convert to GtkContainer
Need to get timezone/DST settings from system
Update for GNOME Shell 3.12
Update according to Notification.addButton API change
Change preferences icon to system-preferences-symbolic
Hide date menu when setting extension preferences
Changed settings button to match with GNOME Shell 3.10 style
Use setAction instead of addButton to add stop button
Connect dateMenu._date 'clicked' signal to toggleDisplayDate method

It is sort of awkward to have it connected to the native method (which
sets date on calendar to current date), and also to toggleDisplayDate,
but I didn't have a better idea.
Use global.play_sound_file/cancel_theme_sound to play stop azan file

This removes dependency on GStreamer introspection data