chore(*): remove unused scripts

  bin/cros_update_image.sh
  cros_show_stacks
  image_to_usb.sh
  make_netboot.sh
  mod_image_for_recovery.sh
  update_kernel.sh
fix(*): use /media/state and overlays dir

/mnt/stateful_partition was already a little unruly with
/mnt/stateful_partition/home and /mnt/stateful_partition/var_overlay
serving similar functional purposes.

Then we needed to also add /opt and /srv overlays.

I also have wanted to get rid of the ugly and weird
/mnt/stateful_partition name so lets just have one big move.

/mnt/stateful_partition -> /media/state
/mnt/stateful_partition/var_overlay -> /media/overlays/var
/mnt/stateful_partition/home -> /media/overlays/home

From there we add /media/overlays/srv and /media/overlays/opt
fix(*): move dev_image to overlays

put the dev_image in overlays/usr/local
fix(build_library): symlnks to stateful

add backward compat symlinks to the stateful directory
Merge pull request #60 from philips/move-stateful-around

Move stateful around