[DATABASE] Update "modified" in Managed_DataObject instead of a DBMS trigger

Instead of relying on the MariaDB's ON UPDATE CURRENT_TIMESTAMP trigger update
"modified" attributes in Managed_DataObject. Every raw query that needs
adjusting is adjusted, as they won't update "modified" automatically anymore.

The main goal behind this change is to fix "modified" updates on PostgreSQL.

classes/Oauth_application_user.php

@@ -86,6 +86,7 @@ class Oauth_application_user extends Managed_DataObject
             return true;
         }
         $toupdate = implode(', ', $parts);
+        $toupdate .= ', modified = CURRENT_TIMESTAMP';
 
         $table = $this->tableName();
         $tableName = $this->escapedTableName();