A much-lauded stage performer whose relatively few screen appearances have yielded four Oscar nominations, Jane Alexander first caught the attention of moviegoers reprising her Tony-winning stage role as the white mistress of black boxer Jack Johnson (James Earl Jones) in "The Great White Hope" (1970). For her film debut, the reed-thin, angular-featured actress was nominated for a Best Actress Academy Award.Often cast as forthright, plain-Jane characters, Alexander (nee Jane Quigley) is noted for the seemingly effortless simplicity and unmannered honesty of her work. The daughter of a