gui/3dsetup, gui/psisetup: switch to singleton

Conflicts:
	src/gui/batchepg.cpp
	src/gui/psisetup.cpp
	src/gui/psisetup.h
	src/gui/user_menue.cpp
	src/gui/videosettings.cpp
	src/neutrino.cpp
	src/neutrino.h
neutrino.h: remove forward-declarations no longer needed

Conflicts:
	src/neutrino.h