fix(*): use new stateful_partition location

moving /mnt/stateful_partition to /media/state
fix(scripts/dev_mode): use overlays/usr/local location

move from images/dev to overlays/usr/local so it is all consistent.
chore(configs/tmpfiles.conf): /user is now gone

/home/core/user is now gone. Just delete this entry.
fix(systemd/init-state): add opt/srv

make sure opt/srv get created if they got dleted.
Merge pull request #7 from philips/move-stateful-around

fix(*): use new stateful_partition location