CRM-13644 - make the acl code common across all 3 CMS. Keep DrupalBase as an empty class shell

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* CRM-13644: ACL does not protect mailing groups in civiMail in Joomla
  http://issues.civicrm.org/jira/browse/CRM-13644
Merge pull request #1852 from dlobo/CRM-13644

CRM-13644 - make the acl code common across all 3 CMS. Keep DrupalBase as an empty class shell