Low mortgage interest rates combined with more affordable housing for families in the median income range are expected to help the real estate market rebound in 2012, economists say.  Fiserv, a financial information services firm, predicts that 95 percent of the 384 metro areas it tracks will see prices rise in 2012.  Many surveys and economists are forecasting a very modest increase for the housing market after several years on declining housing prices and rising foreclosures.