IntensityDataPropertyWidget now works with the Qt signals, emitted by DataItem, IntensityDataItem and axes items.
The old mapper system is hold for a while, it can be switched using USE_MAPPERS macro definition.
Currently the code looks less concise and more ugly than before due to the code duplication (mappers/signals). Also the access of SessionItemWidgets to the JobItem is done in ad hoc manner and should be refactored.