This is still not feature complete, so the page is not linked from
anywhere. It supports graphing benchmark results that match any
perf query. One line is shown per matching benchmark name. Demo
available at:

https://quentin.perf.golang.org/trend?q=upload:20170127.25

Big TODO tasks:
- improve display of multiple benchmarks (multiple graphs?
  click-to-select? additional user controls?)
- correlate benchmarks across uploads (currently all uploads are
  assumed to be from identical machines)
- optimize/cache queries (6 months of a single benchmark loads in 12s;
  6 months of all benchmarks times out at >60s)

Change-Id: I7d1f6073c4837ef63205a10dd4e18085fe7d00ac
Reviewed-on: https://go-review.googlesource.com/36612
Run-TryBot: Quentin Smith <quentin@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>