Copy Data of Custom fields from PurchLine to PurchaseOrderVersions

1. Add fields by using table extensions to the PurchLine and PurchLineHistory tables.
2. Create a new table map containing the fields that must be copied. 
3. Implement the new table map on the two new table extensions.
4. Create a new class to implement the PurchLineIVersioningFieldSet interface and implement the following required methods.
• copyVersion method - Copies data between two records of the new table map type.
• fieldSetTableMapId method - Returns the ID of the new table map.
• isChangeConfirmationRequired method - Returns true or false based on whether the change to the newly added field values requires a confirmation to be created.
5. Now run build + sync.