This commit moves the kernel package version override from the base nixos service to specific system configurations. Now, the latest linux packages will be used only in the system configurations where the override has been explicitly added. This approach gives us more flexibility to handle different kernel package versions for different systems.
This commit includes gnome.cheese and pstree to the list of default services in the gui module. Users will now have these services available by default in the graphical user interface.
Harald Hoyer