Merge branch 'stable-2.15'

* stable-2.15:
  Allow storing audits into a separate file
  Extract audit configuration into a separate class
  Rename 'renderer' to 'format'
  Move CSV-specific classes into CSV-renderer
  Support audit events rendered as JSON string
  Extract Guice Module into a new file
  Extract the object o string rendering engine
  Extract AuditWriter and make the plugin testable
  Fix audit object class to RpcAuditEvent

Change-Id: I6105cc65622721bf688340b4ac706577732b7ff9