[8u60] 8085937: add autoimports sample script to easily explore Java classes in interactive mode

[A. Sundararajan]

Please approve.

Bug: https://bugs.openjdk.java.net/browse/JDK-8085937
jdk9 review thread: 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2015-June/004691.html
jdk8u-dev webrev: http://cr.openjdk.java.net/~sundar/8085937/8u60/webrev.00/

Not backported 'as is' since there jrtfs file system walking cannot be 
used in jdk8. Using rt.jar walking instead. Rest of the autoimports.js 
is same code. CC'ing nashorn team for additional review.

Thanks,
-Sundar