RegionChooser: remove dead code.
command/cloudformation: add StackEventSource utility class.
module: use stack id instead of name when deleting a stack.
command/cloudformation: add formatStackEvent().
command/cloudformation: use Guava EventBus to update stack events.
util: remove unused S3Utils.
command/cloudformation: add TODO about formatting ugliness.
command+util: move StackUtils bxt.command.cloudformation => bxt.util.
util: remove unused AWSOptions.