jshell tool: opinions sought -- double-dash long-form command-line options

[John Rose]

FWIW I used a compact table driven approach to CLI options in the pack200 tool. It might help here. Not a library, just a self-documenting code pattern.

http://hg.openjdk.java.net/jdk9/jdk9/jdk/file/c7550333c4ba/src/java.base/share/classes/com/sun/java/util/jar/pack/Driver.java#l434

I agree with the trend to more modern option syntax. 

– John