CRM-14227 - add Order By Registration Date to Participant Listing report.

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* CRM-14227: Enable sorting the participant listing report by register date
  http://issues.civicrm.org/jira/browse/CRM-14227
Merge pull request #2553 from davecivicrm/CRM-14227

CRM-14227 - add Order By Registration Date to Participant Listing report...