Data Object Modeller: Add the ability to initialise properties

Hi Walter, there was talk on [drools-usage] about using a class authored with the Data Object Modeller and a collection field was null since neither the constructor or setter methods could be invoked in a "no code, low code" environment. I wonder whether it'd be useful to add support for initialising properties with the graphical form of the editor (i.e. not reverting to the source tab). WDYT?