RFR 8159111: JShell API: Add access to wrappers and dependencies

[Robert Field]

Please review --

Bug:
     https://bugs.openjdk.java.net/browse/JDK-8159111

Webrev:
     http://cr.openjdk.java.net/~rfield/8159111v0.webrev/

Spec:
     http://cr.openjdk.java.net/~rfield/jshell_8159111/

     Specifically --
http://cr.openjdk.java.net/~rfield/jshell_8159111/jdk/jshell/SourceCodeAnalysis.SnippetWrapper.html
http://cr.openjdk.java.net/~rfield/jshell_8159111/jdk/jshell/SourceCodeAnalysis.html#wrapper-jdk.jshell.Snippet-
http://cr.openjdk.java.net/~rfield/jshell_8159111/jdk/jshell/SourceCodeAnalysis.html#wrappers-java.lang.String-
http://cr.openjdk.java.net/~rfield/jshell_8159111/jdk/jshell/SourceCodeAnalysis.html#dependents-jdk.jshell.Snippet-
http://cr.openjdk.java.net/~rfield/jshell_8159111/jdk/jshell/ErroneousSnippet.html#probableKind--

Thanks,
Robert