Bump polymer to 0.13.0+1
Add missing widgets to spark_widgets.dart
Add/rearrange widget registration in spark_bootstrap.dart
Add spark-icon to the registration process
Add/rearrange widget registration in spark_bootstrap.dart
Bump Polymer version further
Fix the registration order (turned out to be important)
Attempt to get rid of spark_bootstrap.dart
Finally get rid of spark_bootstrap.dart by using proper Polymer startup procedure
Merge remote-tracking branch 'upstream/master' into polymer-0.13.0

Conflicts:
	ide/pubspec.yaml
	ide/web/spark_bootstrap.dart
	widgets/pubspec.yaml
Merge pull request #3341 from ussuri/polymer-0.13.0

Upgrade to Polymer 0.13.0