An interface that allows for processing the task progress in different ways.
The first time we process the import XML file, we don't know exactly how big it is.
But we know how many entity types there are.
So that time we use the "EntityType" processor and it just tells us the percentage completion of entity types.
On the other hand, The second time we process it, and when we process the partitioned files, we can have counted
the total number of entities,and use these numbers for a more accurate "percent done".