CRM-13148 Support use of cid=0 and cid=NNN for online contribution pages.

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* CRM-13148:
  http://issues.civicrm.org/jira/browse/CRM-13148
Merge pull request #1326 from davecivicrm/CRM-13148

CRM-13148 Support use of cid=0 and cid=NNN for online contribution pages...