Mayor Vincent C. Gray announced Monday that a new ink-jet manufacturing plant will bring 300 new jobs to Ward 8 and that several new restaurants and shops will give a boost to a waterfront development near Nationals Park. The announcements came as Gray (D) delivered a 26-page speech that advisers said was designed to refocus his administration on jobs and economic development and to distance himself from controversies that have taken a toll on his first six months in office. Reading from prompters at a lumber shed at the Yards Park on the Southeast waterfront, Gray outlined plans to lower an unemployment rate that is as high as 25 percent in some D.C.