Manage multiple displays via disper: switch, extend, clone. Requires disper to be installed. Installation: sudo apt-get install disper
Note: Binary files aren't shown on the web site. To see all files, please download the extension zipfile.
Did you know that you can do most of this using XRandR and libgnome-desktop? Also, did you know that you can send simple notifications with Main.notify() instead of spawning notify-send? Ok anyway.
I will look into using XrandR and libgnome. That makes more sense to me since most systems will not come with disper. I have another Cinnamon applet I am moving to an extension but once I am done I will take a look at changing the dependencies.
Disper Displays