Comment 7 for bug 1394338

According to
http://worldofgnome.org/opening-a-new-terminal-tabwindow-in-gnome-3-12/ ,
this is a deliberate change. You have to go into Edit/Preferences/General to
control whether "Open Terminal" opens the terminal in a new window or a new
tab, if you want to use the menu item (or use the hidden keyboard shortcuts
to choose either one, if you can discover them). I didn't think the original
menu was that bloated.