A patch from Pierre Smits for "Service to check UomConversionDated is missing" https://issues.apache.org/jira/browse/OFBIZ-5638

While there is a service to check the existence of a record in UomConversion the equivalent to check the existence of a record in UomConversionDated (mainly used for foreign exchange rates) is lacking.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1595768 13f79535-47bb-0310-9956-ffa450edef68