code: function getService(serviceName) {
  		var serviceData = services[serviceName];
  
  		if (serviceData) {
  			if (!serviceData.instance) {
  				serviceData.instance = serviceData.creator(application);
  			}
  
  			return serviceData.instance;
  		}
  
  		return null;
  	}
docs: Returns the requested service
  @param {string} serviceName The name of the service to retrieve.
  @returns {!Object} An object if the service is found or null if not.
  @private