Eclipse plugin archiving -small revision

[Marshall Schor <ms...@schor.com>]

Because the archive site never erases any files, and because at some time in the
past, the eclipse update site had an "index.html" file generated, this is what
is being fetched when you go to the top level composite update site.

It's left over from a long time ago, before we had a composite site.

It can't be loaded by most browsers, except for firefox.

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The revision to the archive plan - no longer rely on users browsing this archive
composite site to locate the right version-ranged-subsites to use; instead make
an additional website file which just has links to the archived versioned subsite.

I'll proceed with this approach, unless someone objects.

-Marshall