[0.85] #4385: Improve CommonDBRelation factorization to allow User_Group and many more


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@21538 35612d4c-9d10-0410-837c-bf9dd1be60d7
[0.85] #4385: Little fix of previous


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@21539 35612d4c-9d10-0410-837c-bf9dd1be60d7