Issue 107 - Duplicate message checking

[amcghie]

• Introduced a new FailedMessageProcessor interface with a number of concrete implementations. The default behavior is now:
  • A message with a duplicate JMS Message Id will be logged and disregarded
  • A message with a duplicate Failed Message Id will be updated and re-processed again by the system.
• Added an endpoint (/core/admin/jms-listener/read-messages/{brokerName}) to allow on-demand execution of any read-only Queue Browser.
• Remove the createUsersAndRoles configuration from travis build (now executed prior to the test phase)