Document special service resources

[arlimus]

No description provided.

[srenatus]

Note that something's here already https://github.com/chef/inspec/pull/463/files

[chris-rock]

The following is missing in our current service https://github.com/chef/inspec/blob/master/docs/resources.rst#service documentation:

• launchd_service https://github.com/chef/inspec/blob/master/lib/resources/service.rb#L742
• bsd_service - https://github.com/chef/inspec/blob/master/lib/resources/service.rb#L742
• sysv_service - https://github.com/chef/inspec/blob/master/lib/resources/service.rb#L698
• systemd_service - https://github.com/chef/inspec/blob/master/lib/resources/service.rb#L654

Those should be added to the Override the service manager section.