PreOS code did not use configuration support. This fix adds support
for using cdist configuration, which takes into account cdist
configuration file, environment variables and command line options,
especially conf_dir.

It also adds support for -g, --config-file option, for specifying
custom configuration file.

__acl: rename --acl to --entry for the sake of consistency, add compatibility

See merge request ungleich-public/cdist!829

rewrite __mysql_database, add types __mysql_user and __mysql_privileges

See merge request ungleich-public/cdist!827

Add cdist info command

See merge request ungleich-public/cdist!825

__postgres_*: use delimited identifiers (double quoted) in generated SQL

See merge request ungleich-public/cdist!826

Signed-off-by: Steven Armstrong <steven@icarus.ethz.ch>

shellcheck* targets were always reporting exit status 0.
With this fix, if shellcheck fails, then build-helper script
exits with 1.

[new-type] __openldap_server

See merge request ungleich-public/cdist!822

[type-docs] __start_on_boot: remove unspported *BSD claim.

See merge request ungleich-public/cdist!823

The type appears to support {Open,Free}BSD properly.

It's nicer to have slapd_flags after slapd_enable in rc.conf on freebsd.

This already takes care of setting up the base DN and managing it as well as
allowing for settings for the listener URLS.

The type was also made a singleton as it doesn't make much sense to setup
multiple LDAP servers on the same machine.