A patch from Deepak Dixit for "The updation and deletion of content meta data tab is not working.Needs a change of entity ContentMetaData." https://issues.apache.org/jira/browse/OFBIZ-4927

MetaDataValue is changed from primary key to non primary key as the value can be updated.

git-svn-id: https://svn.apache.org/repos/asf/ofbiz/trunk@1633100 13f79535-47bb-0310-9956-ffa450edef68