support for HTML5/Microdata elements

support for HTML5/Microdata elements

Patch let us handle the <data>, <time>, <meta>, and <link> elements.

* handles one part of bug 32545 requesting us to support the <time>
  element in WikiText.
* Partially fix bug 28776 about whitelisting global HTML5 semantic
  attributes and inline meta element.
* <meta> and <link> are only permitted when Microdata is enabled using
* the global $wgAllowMicrodataAttributes. For for security reason, the
  links are only allowed to be actual elements when they have a
  strict set of attributes set.

Change-Id: Ica11be186bd62eb154e1ebc400acb515c10fb65f