Switch to JDK9 Module packaging and compiling

[eeverman]

No description provided.

[rupeshA]

@eeverman , just saw that JDK 9 is already at End Of Support , do you really want to do this?
https://www.oracle.com/technetwork/java/javase/downloads/jdk9-downloads-3848520.html

[eeverman]

@rupeshA There are some pretty major changes from Java 8 to 9. I wrote a short summary of the impact on AndHow:
https://sites.google.com/view/andhow/user-guide/java9

The goal of this task is to switch to the new Java 9 style packaging, not necessary to require Java 9 specifically.

Choosing the right time to make this switch is important: Using Java 8 to compile AndHow allows it to continue to work for Java 8 projects (and there are a lot of Java 8 projects). Switching to Java 9 module style packaging means that it will no long work for those Java 8 projects unless we maintain two builds.

I think the project is not quite ready to make this switch - I would like to bring a few fixes and API changes into a Java 8 release before leaving Java 8 compatibility behind. Please wait before doing work on this task - It will probably be a few months before we are ready for this.

[code4t2]

Related PR: #449