@Override
	public final boolean isReference() {
		return true;
	}
Represents a simple job reference. In the example spec "<tt>aa || bb</tt>" both <tt>aa</tt> and <tt>bb</tt> would
be represented in the AST as JobReference nodes.

@author Andy Clement
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/job/dsl/JobReference.java