Review Request JDK-8181696: Package versioning link does not exist in JAR file specification

[Mandy Chung]

http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8181696/webrev.00/

This removes the reference to the package versioning link as the document [1] does not have too much value.  It includes @implNote to clarify the packages in the system module that don’t have versioning information.

Mandy
[1] http://download.java.net/java/jdk9/docs/technotes/guides/versioning/spec/versioning2.html#wp90779