ServiceNow Integration

Completed ServiceNow integration with nexpose_ticketing.  Includes three major functions (creating new tickets from Nexpose data, updating existing tickets when using IP-address mode, closing tickets that no longer exist in the Nexpose interface).

Also modified the JIRA helper to not break with the new method names.  Note that the JIRA helper should work exactly as before and the service will only attempt to update/close tickets if the helper class responds to the appropriate method.