Better error message for git push failure.
Show authetification failure message on push failure.
Add errorAction button on error dialog.
Improvements in error action dialog.
nits.
Rename http exceptions.
Use askOkCanel dialog and revert changes to errorDialog.
Add action to ok button in okcancel.
Addressed comments.
Merge branch 'master' into git_push_auth

Conflicts:
	ide/app/lib/exception.dart
	ide/app/spark.dart
Merge pull request #2459 from dart-lang/git_push_auth

Git Authorization on push