analysis/appengine/template: improve label display

The display now shows the top N labels, and shows common labels
separately. Each label is a link that filters the results based on
that label.

Also fixes a typo and removes a harmless double Close.

Change-Id: I25b93c7bbfd584ad345c4508e64cd5db73298745
Reviewed-on: https://go-review.googlesource.com/35675
Reviewed-by: Russ Cox <rsc@golang.org>
3 files changed