Add an alternative version of Polymer-based UI + enable switching between UIs.

Not checking in the full up-to-date Polymer-based UI yet to simplify reviewing.
Reuse spark.css in spark_polymer.css
Small non-functional changes/fixes
Go back to calling webkitStartDart(): doesn't cause problems anymore

...Probably after some fixes in Polymer 0.8.5.
Fixed library name in pubspec.
Layout of directories for UI code
Merged
commit drone.io build script
fix to script
more script tweaks
Merge pull request #88 from dart-lang/drone-script

Drone script
Removed spark_polymer_bootstrap.js
Conform to the latest breaking changes in Dartium and fixes in Polymer Dart

1) Single *.dart script tag per HTML is required by Dartium now.
2) Polymer now allows only 1 main() per app, and that used to be taken by init.dart.
3) However, Polymer also fixed an bug around that, and now <script src='init.dart'> can be replaced with initPolymer() in the app's own main().
Added the new spark_polymer.html to dart2js compilation step.
Add spark_polymer.html to the deploy step
Merge pull request #82 from ussuri/ui-in-polymer

Add an alternative Polymer-based UI + persist window geometry between launches
Merge pull request #84 from dinhviethoa/83-UI-directory-layout

Layout of directories for UI code
re-swizzle build
Merge pull request #90 from dart-lang/run-tests

re-swizzle build
Update grind.dart

TBR fix path to the archive file