-- CRM-12809 #1, #2 and #3

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* CRM-12809: Reserved CustomGroups
  http://issues.civicrm.org/jira/browse/CRM-12809
-- CRM-12809 fix for point no 4

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* CRM-12809: Reserved CustomGroups
  http://issues.civicrm.org/jira/browse/CRM-12809
CRM-12809 - For public screens, use phrase "custom field-set"

Per michaelmcandrew, "custom group" shouldn't appear in docs or web UI

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* CRM-12809: Reserved CustomGroups
  http://issues.civicrm.org/jira/browse/CRM-12809
CRM-12809 - Determine is_addable on server-side

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* CRM-12809: Reserved CustomGroups
  http://issues.civicrm.org/jira/browse/CRM-12809