[Caja] Some simple changes that double the speed of HTML rendering.

[mikesamuel]

Reviewers: metaweta,

Description:
Reworks Nodes.render.
Still need to profile and speed up the HTML escaping.

Please review this at http://codereview.appspot.com/116041

Affected files:
  M     src/com/google/caja/parser/html/Nodes.java
  M     src/com/google/caja/plugin/templates/Localizer.java