Added support for parsing external CSS stylesheets.
Improved external CSS loading to first try relative paths.
Improved CSS style rules to parse individual selectors, added support for element and identity selectors.
Improved the handling when the CSS file isn't found by the usual methods.
Merge commit '499b34c536ad855b7664b211740e456460694aa9' into 1.x

* commit '499b34c536ad855b7664b211740e456460694aa9':
  Added support for parsing external CSS stylesheets.
Merge commit '9d364bd2e78d748074cd8710a9e5f56974321bfa' into 1.x

* commit '9d364bd2e78d748074cd8710a9e5f56974321bfa':
  Improved external CSS loading to first try relative paths.
Merge commit '2481673bf6bfbf12da4702fa2ac7460da1c1c861' into 1.x

* commit '2481673bf6bfbf12da4702fa2ac7460da1c1c861':
  Improved the handling when the CSS file isn't found by the usual methods.
  Improved CSS style rules to parse individual selectors, added support for element and identity selectors.
Moved changes out of core DOM classes.