ja: sync to en

ja: sync to en

* ja/index.html: HTML validation for 'meta', 'img', 'br', tags.
  Never translate title parameters in URL.
  Fix ampersands in HTML query parameters.
  Add/fix to match comments in en/ version.
  Add newlines to match en/ version.
  Add b tag to match en/ version.
  Add link to edward source code.
  Use original jplusplus.png as inline image (no localize need).
* ja/mac.html: Likewise.
* ja/next_steps.html: Likewise.
* ja/windows.html: Likewise.
* ja/infographic.html: Likewise.  Update to 3.0.