[0.85] #4385: propose the deletion of CommonDBRelation when both items are of the same type


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@21533 35612d4c-9d10-0410-837c-bf9dd1be60d7
[0.85] #4385: Fix add document to a document


git-svn-id: https://forge.indepnet.net/svn/glpi/branches/0.85-work@21534 35612d4c-9d10-0410-837c-bf9dd1be60d7