Makes it easier to clean any unwanted sites

* No more if.
* Allow lookup to set default value for all docroot
* updated pillar.example

unless test -d on file.directory seems useless.

Support for DocumentRootUser and DocumentRootGroup

Templates already fallback to SiteName before site id.

This attemps to be consistent with them, and avoid having to explicitly specify
the DocumentRoot, when the template already does the proper inference.

This reverts commit 429039819d.

in pillar add 
RedirectMatch: true

Adapted log format to Apache's new default

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

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

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

* Add support for proxy pass target options

* Add example usage

- This is then ignored by Apache

Correct handling of allow encoded slashes

This is done by split the interface pillar value instead of using a proper
list so it behaves exactly the same as before for simple 1 interface cases
(no need to refactor one's pillar files).

The resulting is something like:

  Listen 1.2.3.4:80
  Listen [2001:abc:def:100::3]:80

  <VirtualHost 1.2.3.4:80 [2001:abc:def:100::3]:80>
  ...

Apache2 docs state this is global, but vhost overrides it even when not specified.

additionally, this directive is defaulted differently across distributions (eg. CentOS is default 'On')

this change allows control of the directive.

Add `onlyif` check to execute `a2dissite` only when needed.

DocumentRoot is useless for a plain redirect or proxy vhost, no need to
force creating the directory.

Signed-off-by: Julien Cristau <julien.cristau@logilab.fr>