Maintenance and harmonizations

* Specify deployment top level domain, e.g. webplatform.org, webplatformstaging.org, etc.
* Keeping same DocPad version as specs.webplatform.org
* Changing origin of a few assets to www instead of docs
* Making sure all origin names are consistent, and protocol relative
* Importing error pages for Fastly
* Remove use of base tag, so we can use same html for webplatformstaging.org
* Error page consistency
* Fixing issue when two sso.js are run in same view webplatform/notes-server issue #17
* Making sso.js the same on github.com/webplatform/mediawiki repo
* Importing w3c20 svg logo

Change-Id: I63b9cffa92acf70cc2c81d4ce8b9cba584fa0a4a