Fixed issue #50 (Invalid job progress statistics in case a subsystem fails after another one of the same scene ID already succeeded in the same mapper) by adding class attribute GMS_object.proc_status_all_GMSobjs and GMS_object.proc_status() property. Added gms_object.update_proc_status() decorator.
Revised exception handler. Improved test_exception_handler module.
Fixed a severe bug that copied the same dataset list to all subsequent process controllers.
Former-commit-id: cd572222
Former-commit-id: 0cce191d