civicrm-47 Update to 4.7.28

civicrm/CRM/Activity/BAO/Activity.php

civicrm/CRM/Activity/Form/Activity.php

civicrm/CRM/Activity/Form/ActivityFilter.php

civicrm/CRM/Activity/Page/AJAX.php

civicrm/CRM/Admin/Form/Extensions.php

civicrm/CRM/Admin/Form/Options.php

civicrm/CRM/Admin/Page/Extensions.php

civicrm/CRM/Batch/Page/AJAX.php

civicrm/CRM/Case/Form/ActivityToCase.php

civicrm/CRM/Contact/BAO/Contact.php

civicrm/CRM/Contact/BAO/Contact/Utils.php

civicrm/CRM/Contact/BAO/Group.php

civicrm/CRM/Contact/BAO/Query.php

civicrm/CRM/Contact/BAO/SavedSearch.php

civicrm/CRM/Contact/Form/GroupContact.php

civicrm/CRM/Contact/Form/Search/Custom/ContribSYBNT.php

civicrm/CRM/Contact/Form/Task.php

civicrm/CRM/Contact/Form/Task/PDFLetterCommon.php

civicrm/CRM/Contact/Import/Parser/Contact.php

civicrm/CRM/Contact/Page/DedupeRules.php