base: fixing some HTML5 markup.

* using meta content-type is redundant. See: http://code.google.com/p/doctype-mirror/wiki/MetaCharsetAttribute
* using meta element to specify document-wide language is obsolete.
* link rev is obsolete. See: http://www.whatwg.org/specs/web-apps/current-work/multipage/obsolete.html#attr-link-rev
base: validator says: "Stray end tag link"

link are not like script tags.
base: nav has already role=navigation.

"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."
* http://www.w3.org/TR/html5/dom.html#aria-usage-note
* http://www.w3.org/TR/html5/sections.html#the-nav-element