Dwight D. Eisenhower, the first president to appropriate a White House lawn for golf practice, here completes a pitch shot to an imaginary green. The green is no longer imaginary. A real one was recently constructed outside the President's office. It has a small sand trap on one side, two undersized holes, deliberately made that way to help Ike sharpen his putting eye. Other sports facilities at the White House: F.D.R.'s swimming pool and a bowling alley installed during the Truman administration.