Passing options to the JVM

I need to set explicitly the -Xmx parameter for the JVM to run inside an LXC container, because by default it is picking up the amount of memory installed in the host system (via /proc filesystem), thus exceeding the memory limit set for the container.
With this patch I am able to set whatever options the JVM needs with the JAVA_OPTS environment variable, which is honored also by Jruby and by most Java software init/wrapper scripts.