CentOS 6 reports as CentOS-6 rather than CentOS Linux-6 from osfinger grain

with salt-ssh-2016.11.3 it errored out with
TemplateNotFound: apache/map.jinja

and we were already passing in the 'apache' data as 'map'
from standard.sls

because it requires mod_logio to be enabled

sysconfig.d/global.conf is re-written by sysconfig on openSUSE

According to the pillar.example file there is no site.ProxyPassTarget,
so ProxyPassReverseTarget should default to proxyargs.ProxyPassTarget
(ie. site.ProxyRoute.ProxyPassTarget)

If MaxRequestWorkers is greater than 256 than you also need to set the
ServerLimit value which is defaulted to 256 but has a 20000 hard maximum

* Adding exclude_listen_directive option

* Updating Debian config

* RedHat: Made AddDefaultCharset Directive configurable

* Added description of apache:lookup:default_charset to pillar.example, sane default equals former hardcoded UTF-8

In 4d04d95b02 (#113)
apache/vhosts/standard.sls has been modified by @genuss to include
apache.config on the basis that apache.config was now able to retrieve the
interfaces/ports from pillar data in apache:sites.

I use apache:sites to register virtual hosts with non-standard
"template_file" (they contain the desired configuration directly)
and the "interface/port" keys are thus not meaningful.

apache:
  sites:
    example.com:
      template_file: salt://vm/example/apache-vhost.conf
      DocumentRoot: False

The generated ports.conf ends up containing only "*:80" while
my virtual host configuration files need ports 80 and 443. The
situation was perfectly fine up to now because the default configuration
file handles both of those ports if you have mod_ssl installed.

People who want to use apache.config should just explicitly include
that state, we should not force its usage to all apache.vhosts.standard
users.

* Add ProxyRequests directive

This allows or prevents Apache httpd from functioning as a forward proxy server.
[See](https://httpd.apache.org/docs/current/mod/mod_proxy.html#proxyrequests).
The default action is off so I've set this a the default for this formula so it does not change the default behaviour.

* Add example pillar usage