Display chroot names and details

Add option '-a' to operate on all chroots and '-l' to list croutonversion details.
This isn't the right place to put this.  Unfortunately the logic that already exists in edit-chroot isn't very clean.  The issue is that edit-chroot actually allows and attempts to process multiple commands simultaneously, sometimes in strange ways.  I.e., you can restore, move, encrypt, and backup your chroot simultaneously, but it'll always happen in the order "backup, restore, encrypt, move" (so it'll back up your chroot before restoring it, then it'll encrypt, then it'll move the result).  And if you try to backup and delete a chroot, it'll delete and not backup :(  (the latter could be easily fixed, I guess).

Anyway, I see why you inserted it where you did; ideally we don't unmount the chroot right before attempting to run croutonversion (which needs it to be mounted).  But if any command other than "restore" is present, we need to unmount first.

So here's what I think we should do for now:

1. Move the listing code to above L253 (`if [ "RESTORE" ...`)
2. Always print out the line "name: $NAME"
3. If -ll is specified and the chroot is encrypted, run "$BINDIR/mount-chroot" and capture the error if it fails (mount-chroot will silently succeed if the chroot is already mounted).
4. Follow it up with a line "encrypted: x", where x can be "no", "yes, protected", or "yes, accessible".  The last one you can tell by if "/var/run/crouton/$CHROOT" exists.
5. If mount-chroot didn't fail or the chroot isn't encrypted, follow up with the call to enter-chroot, but with the magical environment variable CROUTON_NO_UNMOUNT=1, which tells enter-chroot not to unmount the chroot.  Don't forget to use the local version enter-chroot (important if the installer is going to call this), pass the chroots dir, and quote the name and whatnot.  The call should look something like this: `CROUTON_NO_UNMOUNT=1 sh -e "$BINDIR/enter-chroot" -c "$CHROOTS" -n "$NAME" -x /usr/local/bin/croutonversion`
6. Let this block run its course, which in most cases will result in unmount-chroot being called.

This should also get rid of the duplicate calls to enter-chroot.