Fixes #8705.

LGTM=adg
R=golang-codereviews, bradfitz, adg
CC=golang-codereviews
https://golang.org/cl/142890044

golang.org now serves HTTPS with a valid cert, so it's reasonable
that users should click through to the HTTPS versions of *.golang.org
and other known sites.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/112650043

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/102340044

Remove "References" section.
Remove most articles and redirect to blog.golang.org.
Move /ref/spec and /ref/mem to /doc/spec and /doc/mem.
Remove duplicate links from the remaining
"Documents", "The Project", and "Help" pages.
Defer to the wiki for more links and community content.
Update command reference and mention cover tool.
Add "Pop-out" text to the front page.
Pick one of four videos at random to feature on the front page.

Fixes #2547.
Fixes #5561.
Fixes #6321.

R=r, dominik.honnef
CC=golang-dev
https://golang.org/cl/13724043

I read docs and wrote a crawler + link checker on the plane,
which also checks for #fragments. I'll send that out later
when it's less gross.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/8729050

CL6449105 changed godoc id attributes to ensure uniqueness.
This CL updates links to godoc pages in documents that used
the old id attributes.

R=golang-dev, dsymonds
CC=golang-dev, speter.go1
https://golang.org/cl/7015051

Both of these have replacements.

R=golang-dev, r, rsc, r, adg
CC=golang-dev
https://golang.org/cl/5979046

Fixes #3478.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5986074

        Fixes #3427.
        Part of issue 3424.

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5959045

Fixes #3245.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5905045