Add git clone.
Fix bug in expandTree.
Fix parsing bug in the git request.
Fix bug in sha / bytes conversion.
More work on git clone.
Add UI for git clone.
fix objectstore test.
nits.
Add placeholder test file for git clone.
Addressed comments
Merge branch 'master' into git_clone

Conflicts:
	ide/app/spark.dart
Merge pull request #379 from dart-lang/git_clone

Git clone
Merge branch 'upstream/master'

Conflicts:
	ide/app/spark.dart
Git clone: style improvements + switch to SparkActionWithDialog
Fixed dialogs' primary buttons not being found in non-Polymer UI
Ported Git Clone dialog to Polymer UI
Fixed file list context menu not found/shown in Polymer UI
Fixed element IDs
Temporary fix for dialogs not displaying in Polymer UI

Moved dialogs from top-level Polymer widget to the root of the UI (spark_polymer.html).
Got rid of superfluous aliased variable