[layout] Use FixedLayout inside Group
[layout] Use FixedLayout inside Group

The Group actor should use the FixedLayout layout manager object
to avoid duplicating code.

djdeath/clutter,djdeath/clutter,rkudiyarov/clutter_osx,jigpu/clutter,spatulasnout/clutter,GNOME/clutter,nobled/clutter,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter-android,djdeath/clutter,kerrickstaley/clutter-vala,collects/clutter,jigpu/clutter,djdeath/clutter-multithreaded,kerrickstaley/clutter-vala,heysion/clutter-clone,ebassi/clutter,spatulasnout/clutter,collects/clutter,djdeath/clutter-android,djdeath/clutter,Distrotech/clutter,nobled/clutter,Distrotech/clutter,jigpu/clutter,dlespiau/clutter,collects/clutter,GNOME/clutter,dlespiau/clutter,spatulasnout/clutter,nobled/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,collects/clutter,rkudiyarov/clutter_osx,djdeath/clutter-android,ebassi/clutter,djdeath/clutter-multithreaded,ebassi/clutter,GNOME/clutter,jigpu/clutter,Distrotech/clutter,rkudiyarov/clutter_osx,heysion/clutter-clone,spatulasnout/clutter,djdeath/clutter,heysion/clutter-clone,dlespiau/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,heysion/clutter-clone,jigpu/clutter,GNOME/clutter,collects/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,ebassi/clutter,spatulasnout/clutter,rkudiyarov/clutter_osx,djdeath/clutter,kerrickstaley/clutter-vala