meta/new-web: another revision of the main-page blurb

(In cooperation with everyone who wrote the previous versions.)
meta/new-web: remove unused module
meta/new-web: add info for v6.0 64-bit Debian installers
meta/new-web: adjust all-version download page style
plt-web and meta/new-web: move and extend web-page identity

For Google and Bing tools
plt-web: improve index-page rendering
base: update package version