Migrate static sites into a specialized internal upstream node

[renoirb]

At this time, we copy to frontend node the static websites files, but that should change.

Idea is to follow conventions created in #115 where we have an internal web server listening only to private network and that frontend type servers proxies requests to.

So far we only had the homepage as a static site and it’s hosted on the same VM as MediaWiki.

Maybe its time we aggregate static sites into one "upstream" role like we would do with a dynamic site backend but to serve only static files.

Sites that could benefit:

• webplatform.org
• www.webplatform.**org**
• www.webplatform.**com**
• webat25.org (now static version as of 2015-05-20)
• code.webplatform.org
• ...?

Note Even though specs.webplatform.org are also static html pages, we’ll let a specialized upstream ("upstream-specs") handle them since we have publican who takes care of refreshing the pages. We should therefore not touch specs.webplatform.org/publican in this work item.