CRM-13621 - add ability to redirect to main entry point for public pages

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* CRM-13621: Handle invalid session errors especially for public pages in a nicer manner
  http://issues.civicrm.org/jira/browse/CRM-13621
Merge branch '4.4' of github.com:civicrm/civicrm-core into CRM-13621
CRM-13621 - fix error messages

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* CRM-13621: Handle invalid session errors especially for public pages in a nicer manner
  http://issues.civicrm.org/jira/browse/CRM-13621
CRM-13621 - fix error messages

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* CRM-13621: Handle invalid session errors especially for public pages in a nicer manner
  http://issues.civicrm.org/jira/browse/CRM-13621
Merge pull request #1837 from dlobo/CRM-13621

CRM-13621