Shell scripts must quote environment variables

I first noticed this for ./scripts/prog.sh. It uses the following incantations:

if [ -z $JAVA_OPTS ] ; then
	JAVA_OPTS="-ea -Xmx4g -server"
fi

if [ -z $JAVA_HOME ] ; then
	JAVA=${JAVA_HOME}/bin/java
else
	JAVA=`which java`
fi

However if there is white space in either JAVA_OPTS or JAVA_HOME then these incantations will break.

Also, JAVA should be quoted as used below in case the file path has whitespace (quotes are missing in the original).

"$JAVA" ${JAVA_OPTS} -cp bigdata-jar/target/bigdata-jar*.jar $*

Finally note that JAVA_OPTS MUST NOT be quoted when it is being passed through to Java, so the following is correct.

"$JAVA" ${JAVA_OPTS} -cp bigdata-jar/target/bigdata-jar*.jar $*