Flow difference descriptions for sensitive properties referencing parameters are unclear

With the addition of Parameters, we can now store a sensitive property in the NiFi Registry if the property value is simply a parameter reference. Otherwise the value is still blanked out. However, when a Flow Comparison is done, if a sensitive property goes from being a static value to a parameterized value, the Flow Difference is shown as PROPERTY_ADDED because the value was previously nulled out and non longer is. Likewise, going from a parameterized value to an explicit value shows as a PROPERTY_REMOVED Difference Type, even though the property was not actually removed, it was just changed from a Parameter Reference to an explicit value. We should update the Flow Comparitor to have two new Difference Types, one for a property being parameterized and one for a property be un-parameterized. We also will need to update the DifferenceDescriptor's to make the wording clear.