A group of Shopko workers has signed a letter asking for the severance payments they were originally promised when the company filed for bankruptcy.  A federal judge approved the retailer’s plan to phase out its operations last week and that sets things up for the remaining stores to close by the end of the month.  The 700 former and current Shopko workers are asking the private equity firm which bought the chain 14 years ago to keep the promise.  The payments to those workers were taken out of the plan as it moved through the courts.