docs: cleanup, remove stale material

docs: cleanup, remove stale material

Point https://fd.io/docs/vpp/master/links/index.html at docs.fd.io/vpp
instead of at one specific stale release

Remove https://fd.io/docs/vpp/master/featuresbyrelease/index.html

Remove https://fd.io/docs/vpp/master/events/index.html

Remove dead projects from
https://fd.io/docs/vpp/master/relatedprojects/index.html

Remove unsupported distros from
https://fd.io/docs/vpp/master/whatisvpp/supported.html

Reduce (doxygen) list of test framework doc files to actively
supported releases

Type: docs

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I179966fbbe09ac123e5f2647787a8dea93190b5c