Laura, Laura, Laura. Any way you look at it, Laura Ingalls Wilder is the star of ''Little House on the Prairie, the Musical,'' now at the Paper Mill Playhouse. In the 1930s and '40s, the real Wilder wrote about her 19th-century childhood in the ''Little House'' books, which inspired the heartwarming NBC series. Melissa Gilbert, who played Laura for nine seasons, from 1974 to 1983, is the star attraction at the Paper Mill. And Kara Lindsay, who plays Laura in the musical, is the star performer. [ABSTRACT FROM PUBLISHER]