Upgrade needs to create financial_trxn, financial_item, entity_financial_item records for existing contributions / line_items

The 4.3 upgrade needs to create financial records for existing Completed contributions and line_items AND needs to update line_items to include financial_type_id.

For each contribution record where status = Completed
1. Update all linked line_item rows - set line_item.financial_type_id = contribution.financial_type_id

2. Follow pattern in http://wiki.civicrm.org/confluence/display/CRM/CiviAccounts+4.3+Data+Flow "New offline contribution" starting w/ 2nd "step"
2.1 Insert civicrm_financial_item row for each linked line_item.
2.2 Insert financial_trxn row for the contribution
2.3 Insert the 3 entity_financial_trxn rows as described on the wiki.

NOTE: This is potentially a long-running task so I think we'll need to use queue runner mechanism.