Port first garden-o-matic component over to polymer

1. Add polymer bower json and update app.yaml appropriately.
2. Add 'unsafe-inline' to script-src so that imports work.
3. Add a load warning if you try to load the page without having
ever synced polymer.
4. Convert ui.results.Comparison over to <results-comparison> and
cleanup all code in ui.results.ResultsGrid.

Put results-comparison in it's own file. It makes sense to
put each custom element definition in it's own file and to test it
independently.

Add a top-level ui directory for all the UI related components. When we're
done, we should be able to delete a bunch of the JS files in the scripts
directory and all the CSS files in the styles directory.

NOTRY=true

Review URL: https://codereview.chromium.org/350563002

git-svn-id: svn://svn.chromium.org/blink/trunk@176805 bbb929c8-8fbe-4397-9dbb-9b2b20218538