There is already a partial solution to the problem documented on askubuntu.com.
Unfortunately, it is not working for Ctrl+Alt+F[1-7] keys. There was a solution for that in Ubuntu 13.04 and eralier to enable "Special keys (Ctrl+Alt+key) handled in a server" in Keyboard Layout -> Options -> Miscellaneous compatibility options. There is also a general X11 xorg solution, but does nor work with Ubuntu 14.04 since it has no /etc/X11/xorg.conf. Also, I cannot find the corresponding option in gnome-tweek-tool, which is supposed to be used in this case according to Ubuntu developers.
How do I enable special keys Ctrl+Alt+F[1-7] in the server so that IntelliJ shortcuts work in Ubuntu 14.04?