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.

Sometimes it's necessary optimization in nginx+apache2 environment

Added example shows 503 code instead of "It works!" page.

By reassigning options with `blockreplace` at `/etc/apache2/conf-available/security.conf`, which is linked as conf-enabled by default on Debian packages

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>

* Add apache version (2.2, 2.4) detection based on osfinger (defaults to 2.4).
* Version can be overridden in pillar (for Apache 2.4 on RHEL 6 for example)

- Added more modules and configuration options
 - Renamed sls files to reflect what they do.
 - added mpm options for Debian