Move things to ./common in preperation for factoring out into seperate repo
Add 'common/' from commit 'ec7c29ac90d4f0e9feee20031be048c123e3b54a'

git-subtree-dir: common
git-subtree-mainline: 01a66818799956654630b29dfaab077112aa5f94
git-subtree-split: ec7c29ac90d4f0e9feee20031be048c123e3b54a
Start to use things from common/ instead