Selecting revisions for A/B testing is hard

Selecting revisions for A/B testing is hard
https://bugs.webkit.org/show_bug.cgi?id=141824

Reviewed by Andreas Kling.

Update the revisions used in A/B testing based on the selection in the overview chart. This allows users to
intuitively select revisions based on points shown in the chart. Removed the old select elements used to
select A/B testing points manually.

Also renamed 'testSets' to 'configurations', 'roots' to 'rootConfigurations', and 'revisions' in each root's
sets to 'options' for clarity.

* public/v2/app.css: Reorganized style rules.

* public/v2/app.js:
(App.AnalysisTaskController):
(App.AnalysisTaskController._taskUpdated): Merged updateTestGroupPanes.
(App.AnalysisTaskController._chartDataChanged): Renamed from paneDomain. It's now an observer instead of
a property, which sets 'overviewDomain' property as well as other properties.
(App.AnalysisTaskController.updateRootConfigurations): Renamed from updateRoots.
(App.AnalysisTaskController._updateRootsBySelectedPoints): Added. Select roots based on the selected points
in the overview chart.

* public/v2/chart-pane.css: Added arrows next to the configuration names (e.g. 'A') to indicate whether
individual build requests / test results are shown or not.

* public/v2/index.html: Removed the select element per configuration column. Also moved the select element
for the number of runs as it doesn't belong in the same table as the one that lists repositories and roots.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@180451 268f45cc-cd09-0410-ab3c-d52691b4dbfc