added new test of the filter builder
added new aggregate builder  test
fixed compile errors in the DataManipulationForm class

These were as a result of the change from single filter, sort and aggregate forms to lists of the above.
changed the alternate constructor of AggregateBuilder to an empty constructor
fixed compilation error due to type mismatch
fixed compilation error due to type mismatch
fixed compilation error due to method name clash
fixed type-related compile errors