RFR 8072853: SimpleScriptContext used by NashornScriptEngine doesn't completely complies to the spec regarding exception throwing

[A. Sundararajan]

Please review http://cr.openjdk.java.net/~sundar/8072853/webrev.00/ for 
https://bugs.openjdk.java.net/browse/JDK-8072853

Thanks,
-Sundar