Independent virtual hosts

References augustohp/ansible-role-apache#1

* [x] Each vhost should have their own file.
* [x] A vhost should be present on sites-available and have a symlink on sites-enabled.
* [x] Provide a way of using sites-available and sites-enabled on RedHat.
* [x] Have variable apache_enabled_vhosts to enable desired vhosts.