CRM-13742 conditional display of invite to create your own PCP after com...

...pleting a contribution or event registration as a supporter. Removed redundant code in CRM/Event/Form/Registration.php (pcpSupporterText assigned in buildPcp() for event pages). Fixed query in getPcpBlockStatus which only worked for contribution_page PCPs, not for event pages.

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* CRM-13742: PCP message should not always promise ability to create your own PCP
  http://issues.civicrm.org/jira/browse/CRM-13742