Add WorkOrder record type

Should be added still:
  - item_list should be a WorkOrderItemList
  - order_status should be a WorkOrderOrderStatus
  - partners_list should be a PartnersList
  - sales_team_list should be a SalesTeamList

Full documentation:
https://system.netsuite.com/help/helpcenter/en_US/srbrowser/Browser2014_1/schema/record/workorder.html
Add WorkOrderItemList and WorkOrderItem

A WordOrderItemList and SalesOrderItemList and pretty much exactly the
same, so there's an opportunity to refactor those to move the logic to a
common place.