buildbot package: actually find commits for each build during ingestion

BUG=skia:3125

Review URL: https://codereview.chromium.org/796883002
Create a space for common web assets and a method to incorporate them into a project.

The common space is /res/ and the webtools/webtools.mk will link that into a project at res/common. So that means that HTML Imports that appear in /res/imp/ will be available to a project at res/common/imp.

This CL also moves login.html and scaffold.html into /res/imp, thus removing their former duplication.

BUG=skia:

Review URL: https://codereview.chromium.org/802663002
Clean up UI for Push Server.

Capture of the new UI here:

  https://screenshot.googleplex.com/qXsuBCYPGg.png

Not as large of a change as it looks since most of the detla is changing the order of the element declarations.

BUG=skia:

Review URL: https://codereview.chromium.org/801843002