Initial work on creating mechanism for stopping in progress deploy
Complete actor section of work to stop deploys

 - Refactor logging to enable work to be logged in many separate execution chunks by passing around a logging context
 - Move initial work to extract and resolve context into calling method (currently blocks)
 - Add initial UI implementation to stop deploys
 - Added testing and debugging functionality to show DB representation of a deploy
 - Rename task type case class so it doesn't clash with same class name in magenta
Merge branch 'master' into interrupt-deploy
Improved UI for stopping deploys

 - users now get an immediate response
 - stop buttons disappear after deploy is done
Propagate stopFlag behaviour down to repeated polling checks
Reduce logging verbosity
Use a shared mailbox dispatcher
Further improvements to cancelling deploys

 - Moved preparation into the TaskRunner process
 - Can now cancel a deploy before it starts running
Fix missed change during refactoring
Make the stop flag sticky so a page refresh retains the state
Merge pull request #62 from guardian/interrupt-deploy

Ability to interrupt a running deploy