ISPConfig itself does not read nor interpret this header, but there might be other
server components like PHP that might interact with it so I'll disable it just to be sure.

 - Reason:
   AddHandler fcgid-script .php
   does not only parse .php files, but all .php.* (e. g. .php.txt, .php.test etc.)

- Added function to detect the apache version to installer.
- Added support for apache 2.4 to vhots templates for ispconfig vhost and apps vhost in installer.

- Add config to clear php handler in apps vhost.