Two college kids cart trash to make some cash--and end up creating an empire.By Lynn RoselliniIt's the universal cry of parents, generally heard by the second day of college breaks: "Get a job!" Omar Soliman's mother joined the chorus; she was not about to have her son hanging out at the neighborhood pool all summer. "You have to do something," she told him. Soliman's friends had nailed down prestigious internships in his hometown of Washington, D.C. But Soliman liked to party; he couldn't imagi