8044638: Tidy up Nashorn codebase for code standards
Reviewed-by: lagergren, sundar

8017950: error.stack should be a string rather than an array
Reviewed-by: hannesw, jlaskey

8015855: test/script/basic/JDK-8012164.js fails on Windows
Reviewed-by: hannesw, lagergren, jlaskey

8012164: Error.stack needs trimming
Reviewed-by: lagergren, jlaskey