Make docker-admin a tiny bit easier to use
Migrate Crowbar framework to Rails 4.0

This pull request migrates the Crowbar framework to being a Rails 4 web
app, and does some cleanup along the way.

* Model-based access control (via attr_accessible and attr_protected)
  has been replaced with strong parameter based access control See
  http://guides.rubyonrails.org/action_controller_overview.html#strong-parameters
  for more information on how to use strong parameters. All of our
  models and controllers have been updated to use strong parameters.
* render_error in the application_controller knows how to turn
  ActiveRecord::RecordNotFound exceptions into proper 404 errors, and
  ActiveRecord::RecordInvalid exceptions into 409 errors.  The
  find_key model helper now just adds the model and key we were
  searching for to the RecordNotFound exception if it cannot find the
  object we are looking for.
* find_key has been replaced with find_by wherever applicable when it
  was being called from within a model.  You should now only use
  find_key from within a controller.
* The api_foo methods in application_controller.rb have been
  simplified to rely on render_error catching and handling errors they
  may throw.
* Rails no longer allows you to abuse STI the way we have been doing
  in the past.  The barclamp import process now handles creating
  specialized roles, attributes, and jigs.
Rearrange routes.rb to make deployment_roles helpers generate correctly.
Sanitize node_role partial name when showing noderoles.
Add more cleanup to the pristine-update.sh script.
Zap shell history as part of the cleanup process.
Update docker-admin to refer to our latest Docker image for Centos.

This includes all the updates needed to work with Rails 4.
Merge pull request #54 from VictorLowther/migrate-to-rails-4

+2 Migrate Crowbar framework to Rails 4.0