[docs] Increase verbosity for commit messages
[docs] Increase verbosity for commit messages

Apparently, not everyone read the HACKING file, especially the
section about commit messages. This lead to some confusion with
regards to the acceptable (i.e. mandatory) format for commit
messages in Clutter. Let's clarify it a little bit before I start
enforcing it and reverting commits.

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