CRM-15555 - Fix bug in addPaypalExpressCode function. Clean up Billing required label and add inline help. Fix issue where PayPal fields not picked up on page load in event/register due to missing change in Register.tpl.

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* CRM-15555:
  https://issues.civicrm.org/jira/browse/CRM-15555
Merge pull request #4559 from davecivicrm/CRM-15555a

CRM-15555 - Fix bug in addPaypalExpressCode function. Clean up Billing r...