Also, change local mode to use absolute "file://" references across
sites (makes "doc-site.js" plus "doc-site.css" work locally) and
add "index.html" to paths a needed, but add a `-r` relative mode for
the old behavior.
Separate the "generated resources" part of a site from the "rendered
element" part, so that a site that doesn't use full-page formatting
can take share the resources of one that does.
Also, hide the "resources" function in a site to narrow the interface
exported by `plt-web`.
The "plt-new-services" package defines the "meta/new-web"
collection, with the idea that it will be merged into
"plt-services" and later replace "meta/web".
