[release-branch.go1.7] godoc/dl: change "All versions" to "Archived versions"

This change makes each release show only once on the whole page.
The current stable releases are not shown under the archive.

This change also fixes expandos to work correctly on IDs that are not
valid CSS selectors (i.e., "#go1.7.4") to ensure that the file listing
for a given version is expanded.

Updates golang/go#17574.

Change-Id: I7ff1041be3e0072286772ffa545a124764f81945
Reviewed-on: https://go-review.googlesource.com/34911
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-on: https://go-review.googlesource.com/35096
Reviewed-by: Chris Broadfoot <cbro@golang.org>
5 files changed