CRM-13554

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* CRM-13554: Improve string validation in the query engine
  http://issues.civicrm.org/jira/browse/CRM-13554
CRM-13554 - validate values of limit and offset

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* CRM-13554: Improve string validation in the query engine
  http://issues.civicrm.org/jira/browse/CRM-13554
CRM-13554 - validate values of order by

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* CRM-13554: Improve string validation in the query engine
  http://issues.civicrm.org/jira/browse/CRM-13554
Merge pull request #1758 from dlobo/CRM-13554

CRM-13554