Moved all metadata into the request context for logging.
Removed some no-longer-needed code.
Moved reset_session to the show action to ensure that we'll be able to see the visit_id throughout the confirmation process.
Added a helper method around a hack for setting visit_id.
Merge pull request #4 from ministryofjustice/logstasher-request-context-support

Moved all metadata into the request context for logging.