[ns] web version of ns manual moved and updated

[John Heidemann <johnh@ISI.EDU>]

The web version of ns manual (formerly "ns notes and documentation")
has been moved and updated.

It now lives in
	<http://www.isi.edu/nsnam/ns/doc/>
and should be updated at midnight every day (US West coast time).

In addition, gzip'ed postscript and pdf versions are at
	<http://www.isi.edu/nsnam/ns/doc/ns_doc.ps.gz>
	<http://www.isi.edu/nsnam/ns/doc/ns_doc.pdf>

This change hopefully clears up several problems with the manual
(inaccurate webification of some pages, failure of the automatic
updates, etc.).  Unfortuantely, most of the figures are still broken
in the web version (although correct in both ps and pdf).

(The date in the ps and pdf files should now only change when we add
documentation, not everyday.  The most recent version is labeled "July
7, 2000".  Unfortunately this does not hold for the html version.)

   -John Heidemann