add param to class apache::vhosts

this add the possibility to pass vhosts_defaults to the class for enforcing some site-wide vhost stanards
e.g. via Hiera or to significantly shorten the content of  on nodes hosting many vhosts (puppetlabs#2325)

manifests/vhosts.pp

@@ -13,14 +13,31 @@
 #       },
 #     },
 #   }
-#
+# @example To create a [name-based virtual host](https://httpd.apache.org/docs/current/vhosts/name-based.html) `custom_vhost_1` using vhosts_defaults
+#   class { 'apache::vhosts':
+#     vhosts_defaults => {
+#       'access_log_format' => 'noip',
+#       'priority'          => false,
+#     },
+#     vhosts => {
+#       'custom_vhost_1' => {
+#         'docroot' => '/var/www/custom_vhost_1',
+#         'port'    => 81,
+#       },
+#     },
+#   }
 # @param vhosts
-#   A hash, where the key represents the name and the value represents a hash of 
+#   A hash, where the key represents the name and the value represents a hash of
 #   `apache::vhost` defined type's parameters.
+# @param vhosts_defaults
+#   A hash of `apache::vhost` defined type's parameters used as defaults for one
+#   or more vhosts - this could could be used to set vhosts_defaults on nodes
+#   with many vhosts or ensure site-wide vhosts_defaults in Hiera
 #
 class apache::vhosts (
-  Hash $vhosts = {},
+  Hash $vhosts          = {},
+  Hash $vhosts_defaults = {},
 ) {
   include apache
-  create_resources('apache::vhost', $vhosts)
+  create_resources('apache::vhost', $vhosts, $vhosts_defaults)
 }