Auto-remove /svr-setup directory

123.09beta01 auto purges largest files in /svr-setup related to nginx and php upgrade routines (centmin.sh menu option 4 and 5) only keeping the current + previous version i.e. if you upgrade to PHP 7.0.20, only 7.0.20 and 7.0.19 are kept, all other versions are purged.

Purging all /svr-setup can be tricky

1. It masks your real disk usage requirements. Meaning if you're low on disk free space and /svr-setup is purged, it gives end user false sense of disk free space available. Say if /svr-setup takes up 3GB of disk space and you have 1GB free disk space left. If you purge /svr-setup, end user sees 4GB disk free space. They then use that disk space for site data ~2GB used so now have 2GB free disk space. Then come nginx + php-fpm and other upgrades which require that 3GB disk space will error out and fail to complete as you only had 2GB free disk space.
2. Keeping current and previous version, allows you to recompile nginx and php same versions for when you enable/disable new features without re-downloading them. But what if the official download site is down and you need to recompile ? If you purged /svr-setup completely, you would have access to no local version for recompile and won't be able to download from official site until the site is back online.