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.

Originally developed at ungleich and improved for Open Sourcing by Evilham.

Add conf-dir preos option

Closes #794

See merge request ungleich-public/cdist!821

Add chapter for installing from source with signature verification.
Resolves #795.

[docs] PreOS: English nitpicking

See merge request !820

E.g.

16.10. __block
16.11. __ccollect_source
16.12. __cdist
16.13. __cdistmarker
16.14. __check_messages

insted of

16.10. cdist-type__block(7)
16.11. cdist-type__ccollect_source(7)
16.12. cdist-type__cdist(7)
16.13. cdist-type__cdistmarker(7)
16.14. cdist-type__check_messages(7)

Resolves #796.

Fixes gitlab #790.

[PACKAGE-UPDATE-INDEX]: Bugfix of the alpine part of the __package_update_index type

See merge request !818

Redefine/reimplement CDIST_ORDER_DEPENDENCY

See merge request ungleich-public/cdist!815

Update documentation.

CDIST_ORDER_DEPENDENCY now defines type order dependency context.
cdist (emulator) maintains global state variables, as files,
order_dep_state and typeorder_dep, and per object state variable,
as file, typeorder_dep.

If order_dep_state exists then this defines that order dependency is
turned on.
If order_dep_state does not exist then order dependency is turned off.

If order dependency is on then objects created after it is turned on are
recorded into:
    * global typeorder_dep, in case of init manifest
    * object's typeorder_dep, in case of type's manifest.

If order dependency is on then requirement is injected, where object
created before current, is read from:
    * global typeorder_dep, in case of init manifest
    * object's typeorder_dep, in case of type's manifest.

Every time order dependency is turned off, typeorder_dep files are
removed, which means that type order list is cleared, context is
cleaned.

In the end cdist cleans after itself, i.e. mentioned files are removed.

When running type manifest is finished typeorder_dep file is removed.
When running config finishes global typeorder_dep and order_dep_state
files are removed.

Global type order recording is untouched.
Furthermore, for completeness, type order is now recorded for each object
too.