Review Request: JDK-8180208 Provide a new docs bundle page

[Mandy Chung]

The old docs bundle page (aka layer cake) is legacy and not maintained.  In JDK 9, we replace it with a simple page listing modules by groups.  This page can continuously be improved.

   http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8180208/docs/docs-index.html

This is generated by a build tool.  Webrev at:
  http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8180208/webrev.00/index.html

The makefile generates this page in docs-index.html.

Magnus - we will follow up whether you or I make the change to replace index.html. 

thanks
Mandy