hg.openjdk.java.net project and per-project repository lists

[mark.reinhold at oracle.com]

http://hg.openjdk.java.net now displays a list of Projects rather
than every single repository on the server (or, more annoyingly,
a "503 Service Unavailable" error).

http://hg.openjdk.java.net/$PROJECT now displays a list of all the
repositories for $PROJECT; e.g., http://hg.openjdk.java.net/jdk9 .

The non-root repositories of Mercurial forests are indented so as
to make the overall list easier to read.

Please report any problems to ops at openjdk dot java dot net.

- Mark