Provide a way to customize JAVA_OPTS without overriding the whole command

We would like a way to customize the JAVA_OPTS of each micro-services in the ARender stack without having to change the Docker CMD.

Like it, we can customize the JVM options and tune the instance without the risk to miss a command update in a future ARender version.

Its first usage would be to customize the heap size, and the Fatal Error Log file (files created when the JVM crashes).