Code cleanup: Pipeline utilities now take env and parent frame.

* Removed manager and passed in env and parent-frame to all
  utilities that process content in new pipelines.

* Added more documentation to mediawiki.Util.js.

* Renamed processAttributeToDOM to a more appropriate name.

* Added pipelineFactory property to env and used that to
  construct parsing pipelines everywhere.

Change-Id: Ic612e5630d19d4e3f5d6388bc5cd117d337fd799
Merge "Code cleanup: Pipeline utilities now take env and parent frame."