PRD-4671 & PRD-4564: Removed parameterUpdateText() method as it is no longer needed...

... due to better formula editor logic.  Made ParameterUpdateHandler accessible to test cases as the DRILLDOWN formula is not registered in function registry as it is an extension - so the handler does not get registered.  Having the handler available also lets me fix the testValidateAddingAConstantToSumFunction() failing as indicated in PRD-4564.