CRM-12925 - Search Builder - Allow query-classes to influence the options displayed for each field

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* CRM-12925: Implement "Job" search (for "Search Builder")
  http://issues.civicrm.org/jira/browse/CRM-12925
CRM_Contact_BAO_Query_Interface - More docs
Merge pull request #1495 from totten/master-alter-search-builder

CRM-12925 - Search Builder - Allow CRM_Contact_BAO_Query_Hook to influence options