Create a symbolic link from /usr/local/chroots to /mnt/stateful_partition/crouton:
Makes sure that dev_install does not wipe the chroots.

Also, migrate existing chroots to new directory (transparent to the user, and very
fast as we stay on the same filesystem).
Fixes after review.
Install chroots in /mnt/stateful_partition/crouton/chroots
so we can put other stuff in /mnt/stateful_partition/crouton (e.g. shared directories).
Update edit-chroot

Add 'a' and 'l' options to optionally operate on all chroots and display croutonversion details.
Update main.sh

Display valid chroot names when a chroot with the release name cannot be found.
enter-chroot: Simply bind mount /var/run/udev

Also invert the test (i.e. check for existence of /var/run/udev),
to protect against the very unfortunate case where /var/run/udev
is a symlink to /dev/.udev (update while chroot is running, started
with previous version of enter-chroot). In that case, bindmount
creates /dev/.udev, which is not a problem in itself, but would
break further chroot starts.
Tweaked edit-chroot

Moved 'set $@' logic earlier in script so it gets run sooner.
Added option to specify '-l' twice in preparation for ENCRYPTED chroot logic.
Accommodate encrypted chroots

Added logic to accommodate encrypted chroots when specifying the '-ll' option.
Added output for name validation

When name validation fails, added output of valid chroot names.
Tweaked to set all chroots

Removed check for chroot names entered when the '-a' option is specified.
Revert "enter-chroot: Simply bind mount /var/run/udev" (+ invert test)

This reverts commit 24c160cee85d781d74c0018936936091a64337ad.

Bind mounting in /var/run is really a bad idea: we need to
hardcode the path in installer/prepare/ubuntu, or run another
find/xargs expression.

Bind mounting to /var/host is simpler, and works just fine.
Merge pull request #967 from drinkcat/fix-udev-control-dir-revert

Revert "enter-chroot: Simply bind mount /var/run/udev" (+ invert test)
Merge branch 'chrootdir' of git://github.com/drinkcat/chroagh into chrootdir
Cleanup of chroot directory migration output.

The case where a chroot is mounted is common, so the installer now instructs and
waits for the user to close any open chroots.

mv -T will clobber empty directories and prevent strange things from happening
if the user does something in parallel.
Don't end the line, to show that it's waiting.
Updated edit-chroot per line notes

Changed script to comply with notes from @dnschneid - hopefully. :)
Testing results will follow.
Add note about pressing ctrl-C
Fix warning message output
Update main.sh per line notes

Changed script to comply with notes from @dnschneid - hopefully. :)
Testing results will follow.
Update edit-chroot per more line notes

Changed script to comply with additional notes from @dnschneid - hopefully. :)
Testing results will follow.