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
Import files using drag&drop
cleaned
git nits; move getGitTestFileSystem() into git.dart
Fixed a bug: attributes of some Polymer widgets were malformed
Merge pull request #394 from ussuri/fix-widget-attrs

Fixed malformed attributes in some Polymer widgets
Merge pull request #393 from dart-lang/git_nits

git nits; move getGitTestFileSystem() into git.dart
Fixed style nits in Git Clone

- non-conformant order of attributes in HTML
- non-conformant naming convention for element IDs
- misnamed variable in Dart
- double-vs-single quotes for referencing element IDs in Dart
- something else?
Complete the fix