[explorer/init] Support more init systems

See merge request ungleich-public/cdist!850

[cdist]Update os_version for alpine

See merge request ungleich-public/cdist!849

__update_alternatives: add state explorer

See merge request ungleich-public/cdist!848

Fix password command synthax in __postgres_role

See merge request ungleich-public/cdist!845

[__systemd_service] new type to manage the state of systemd services

See merge request !844

[__cron] Fix cronjob removal if `is` and `should` don't match

See merge request ungleich-public/cdist!841

For more generalisation, the default parameter values are now handled by
cdist instead of trying to get a value and use a default if parameter is
not given.

It handles the default values in a more general way, instead of write
one default in (possibly) multiple places.
Problem occurred when checking the 'state' parameter, which required to
set a default value in two places.

This only allow following cases:
  - present
  - absent
else, it will abort with an error message.

__package_apt: update index cache, on installation, when it is older than one day

See merge request ungleich-public/cdist!842

__mysql_privileges: fix quoting

See merge request ungleich-public/cdist!843

__file/__directory: Patch for systems without stat(1)

See merge request !839

explorer/os_release: Add fallbacks

See merge request !840