Centralize meta information about dss.

Centralize meta information about dss.

This defines a couple of package related variables in Makefile,
renames dss.suite -> dss.suite.m4 and index.html.in -> index.html.m4,
and tweaks the recipes to generate dss.suite and index.html.in from
the m4 files, referring to these variables. The contents of the
README file are moved into Makefile so that the three paragraphs can
be printed with make README.