WIP: change system exec calls to safe variant

interface/lib/app.inc.php

interface/lib/classes/functions.inc.php

interface/lib/classes/system.inc.php

interface/lib/classes/validate_dkim.inc.php

interface/web/mail/ajax_get_json.php

server/lib/app.inc.php

server/lib/classes/aps_installer.inc.php

server/lib/classes/cron.d/100-monitor_email_quota.inc.php

server/lib/classes/cron.d/150-awstats.inc.php

server/lib/classes/cron.d/150-webalizer.inc.php

server/lib/classes/cron.d/200-logfiles.inc.php

server/lib/classes/cron.d/500-backup.inc.php

server/lib/classes/cron.d/500-backup_mail.inc.php

server/lib/classes/cron.d/600-purge_mailboxes.inc.php

server/lib/classes/cron.d/900-letsencrypt.inc.php

server/lib/classes/functions.inc.php

server/lib/classes/letsencrypt.inc.php

server/lib/classes/monitor_tools.inc.php

server/lib/classes/system.inc.php

server/mods-available/remoteaction_core_module.inc.php