This function, in Test and Dev mode will vend the instance of LiftRules.
This function, in Test and Dev mode will vend the instance of LiftRules. If there is an instance set in devTestLiftRulesInstance, that instance will be used, otherwise the global instance in LiftRules.prodInstance will be used.
In Dev and Test mode, there's an option to stuff another LiftRules instance in here and use that one for mocking