CRM-15118 - potential replacement for https://github.com/civicrm/civicrm-core/pull/3872 which did not work in my testing (billing block never hideable).

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* CRM-15118:
  https://issues.civicrm.org/jira/browse/CRM-15118
Merge pull request #3876 from davecivicrm/CRM-15118

We have tested this & it works as expected