Cold wars come in a few sizes, but the warm wars -- the ones that burn and give off a fair amount of long stares and result in exasperation and quivering faces — are the ones that Christopher Porterfield of Field Report worries about on the Milwaukee, Wisconsin band’s third album, Summertime Songs . They’re suntanned and wind-swept. They’ve been crying and they’ve been drinking. These warm wars are the result of chaffing, of friction and boredom. They’re caused by everything and nothing at all,