Merge branch 'cc/codespeed'

"perf" test output can be sent to codespeed server.

* cc/codespeed:
  perf/run: read GIT_PERF_REPO_NAME from perf.repoName
  perf/run: learn to send output to codespeed server
  perf/run: learn about perf.codespeedOutput
  perf/run: add conf_opts argument to get_var_from_env_or_config()
  perf/aggregate: implement codespeed JSON output
  perf/aggregate: refactor printing results
  perf/aggregate: fix checking ENV{GIT_PERF_SUBSECTION}