crush depth

Java 11 and Maven 3.6.0

Java 11 is out, and is the current LTS release (at least if you're using the Oracle JDK).

I'll be moving all of my code to start requiring JDK 11 at a minimum as of now.

Additionally, Maven 3.6.0 is currently in the process of being released, and it contains a fix for an issue that's important to me, so I suspect I'm also going to start requiring Maven 3.6.0 everywhere too.