Enable LDAP support on mediawiki

Users can log in using their LDAP account (in the
ou=users,dc=kosmos,dc=org group and with the wiki attribute set to
enabled)

Add an attribute for the ldap master server, so it can be overridden in
the development environment

Refs #107

environments/development.json

@@ -13,6 +13,9 @@
       "elasticsearch": {
         "allocated_memory": "128m"
       }
+    },
+    "kosmos-dirsrv": {
+      "master_hostname": "localhost"
     }
   }
 }