Add Java 11 Support

[wollf92]

I'd like to see support for Java 9 added. Many features regarding easy types and streams were added and I'd like to use them on codewars like I use them in real life.

Thanks!

[javatlacati]

@wollf92 Do you know which modifications should be in the runner gradle file?

[kazk]

I'll look into adding Java 9 (and JUnit 5) to the new runner after the migration.

[kazk]

Java 11 is now available. I'm planning to run a script to update existing kata, but not today.

[Voileexperiments]

@kazk All Java katas has been updated to Java 11. However all katas that use reflective access will cause unsuppressible warning messages to STDERR since new security features are added to prevent cross-module reflection access starting from Java 9:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by $PERPETRATOR (file:/home/codewarrior/java/classes/) to $VICTIM
WARNING: Please consider reporting this to the maintainers of $PERPETRATOR
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

In general it seems that Java is moving away from any kind of raw reflection usage (though you can still do JVM hacks via class loader and security manager hacks), so I suppose all katas that uses reflection directly might have to be retired at some point.