Cm 10.1

This is probably missing something. 
For instance, I couldn't quite understand if the shades in the system_bar.xml are set for every single button, but I think they are. Anyway, not having this won't prevent the buttons from working.

Volume buttons will also show as back buttons, instead of custom ones. Didn't want to waste time doing that just now.

Plus, the menu button is only visible when an app calls it. But the space used should remain reserved, even if it's invisible.

Give it a look and see if this makes sense! :)