base: fix redundant/obsolete HTML

* using meta content-type is redundant.
  http://code.google.com/p/doctype-mirror/wiki/MetaCharsetAttribute
* using meta element to specify document-wide language is obsolete.
* link rev is obsolete.
  http://www.whatwg.org/specs/web-apps/current-work/multipage/obsolete.html#attr-link-rev
base: fix link tags for stylesheets

* link are not like script tags so they shall not be closed using </link>
base: fix redundant role=navigation on nav tag

* "In the majority of cases setting an ARIA role and/or aria-* attribute
  that matches the default implicit ARIA semantics is unnecessary and not
  recommended as these properties are already set by the browser."
  See: http://www.w3.org/TR/html5/dom.html#aria-usage-note
  and http://www.w3.org/TR/html5/sections.html#the-nav-element
search: required space between HTML attributes