Add READMEs to the most important services

Other stuff may be more specific to our site, their READMEs may be added
later.
Fix stupid typo.
Declare the correct supported version of logstash
add more httpd configuration parameters
invert the refactoring
working httpd.conf on EL6
tested php.conf example
rework auth.tt
rework dirinternals.tt
rename setenvif, extend with other env parameters
refine file_basic
refine global.tt
add kerberos parameters
refine location
refine log
add shibboleth parameters
refine ssl
refine system
refine vhost
refine generic_server