Use '!' as sed separator to avoid possible conflict.
Add install-base script and related support files.

This script allows you to create a base image, installing additional
configuration files and performing post-install customisation to the
seed image.

Files in the `overlay` directory are pre-processed and installed into
the target zone, before the `/root/customize` script is executed in
the zone.
"SmartMachine" is henceforth known as "Instance".
Update JSON for version 2 of IMGAPI.
Update documentation for recent image manifest changes.
Ensure $outdir is defined before used.
Configure syslog.conf and logadm.conf
Configure IMAGE_DOC for SNGL.
Add support for specifying a version number to installed images.

Rather than adding more positional arguments, convert install-base to
a proper getopts implementation.  Substitute the version number in the
appropriate places to the installed system.
DATASET-602 want tab completion for pkgin install

This goes a bit further and adds completion for other pkgin commands too,
as well as completing the commands themselves.
Only generate pkg_install.conf if it doesn't exist.

With newer bootstraps it is included so that pkg_add works out of the
box, so we don't want to overwrite that version.
Ensure pkg_alternatives symlinks are correct.

Without this, the /usr/bin/vi symlink on SNGL was still pointing at
the platform vim and causing errors.