RFR 8068431: @since and @jdk.Exported are missing in jdk.nashorn.api.scripting classes and package-info.java files

[A. Sundararajan]

Hi,

Please review http://cr.openjdk.java.net/~sundar/8068431/ for 
https://bugs.openjdk.java.net/browse/JDK-8068431

Thanks,
-Sundar