more secure unique strings

docs/autoinstall_samples/autoinstall.conf_sample.php

install/dist/conf/centos80.conf.php

install/dist/conf/debian100.conf.php

install/dist/conf/debian110.conf.php

install/dist/conf/debian90.conf.php

install/dist/conf/debiantesting.conf.php

install/dist/conf/gentoo.conf.php

install/dist/conf/ubuntu1604.conf.php

install/dist/conf/ubuntu1710.conf.php

install/dist/conf/ubuntu1804.conf.php

install/dist/conf/ubuntu2004.conf.php

install/lib/installer_base.lib.php

interface/lib/app.inc.php

interface/lib/classes/auth.inc.php

interface/lib/classes/functions.inc.php

interface/lib/classes/remoting.inc.php

interface/lib/compatibility.inc.php

interface/web/login/password_reset.php

server/lib/classes/functions.inc.php

server/lib/classes/letsencrypt.inc.php