do not force directory for external and optional dependencies,return 2 in parse_service_before() if the service is already parsed

Update 66-enable.md

See merge request Obarun/66!52

Update module-service.md

See merge request Obarun/66!49

Update 66-enable.md

See merge request Obarun/66!50

Update frontend.md

See merge request Obarun/66!51

use ss_resolve_t and ss_revolve_svtree to find the configuration file instead of reading directly the sysadm configuration directory. Help user with a good help message in case of sudo command

add rebuild_list(). Place configuration file location of each service inside the module configuration directories version, add MOD_COLOR environment variable at the configure script runtime