fixed server install script to rewrite the default configuration file and not a template, and removed the old config template

centos) as well as debian/ubuntu

Revert "Use the new install script as make install target. Message about install script requiring root changed a bit to make it more evident."
After talking with Pieter he changed my mind about this, it is better to
have a simpler install script that works everywhere, and the complex one
can be always executed if needed by hand. We'll make possibly a new
target for the full featured installation script, and even suggest it
after a Make install.

This reverts commit f1e60d75.

Use the new install script as make install target. Message about install script requiring root changed a bit to make it more evident.