Item and item class tables

The following changes were made to the item and item class tables:

item_attr

The row_id column data type is updated to bigint64 in order to accommodate high transaction volumes on the table. For more information, see item_attr.

item_class_attr

The row_id column data type is updated to bigint64 in order to accommodate high transaction volumes on the table. For more information, see item_class_attr.