add one more shell script header with JAVA_OPTS

Sometimes it is needed to pass arguments directly to JVM. The simplest way to do that is to use environment variable. I see 3 ways to do that:
1) Do nothing and pass jvm args via workaround like prependShellScript = Some(Seq(defaultShellScript.head, """exec java $JAVA_OPTS -jar "$0" "$@""""))
2) Add $JAVA_OPTS to already existing defaultShellScript
3) Create a separate $JAVA_OPTS aware header
I like the 3rd way. But only if my proposal seems to be reasonable enough :)