The eruption of gunfire outside a funeral home on Chicago’s South Side that left 15 people wounded was part of an ongoing conflict involving the gang of a young man being mourned and a rival gang, police said Wednesday as the federal government planned to send more agents to the city to combat a spike in gun violence.Chief of Detectives Brendan Deenihan said the man whose funeral people were attending had been killed in a drive-by shooting last week and that he was killed in retaliation for a previous shooting.Police said …