Added support for unbooting (releasing all associated aws resources) 

Hi Stefan,

Here are the changes to support unbooting. Quick outline of changes below.

- Added Unboot and dev_unboot buttons to scenario show
- Updated scenario_show.js.erb to support decrementing counts as well as adding push support for status
- Removed blank line (before Clouds) in show scenario/show.html.erb as well as making status pushable
- Updated progress fields during boot (add_progress)
- Added unboot method to aws.rb (aws_scenario_unboot)
- Added Strace recipe to cookbook

Have tested mulitple times. Can boot and unboot as many times as you like now. Boot hangs on ocassion, something to do with routes. I think it is probably a AWS timing issue.