For now process is always call. When call from workflow_concept it insure the input has benn provided previously. Otherwise you should provide the xas_object. It might evolve with time.

Add some simple unit test to insure an orangecontrib est workflow can be converted to a graph and a graph to an est workflow.
Add test to insure we can execute it as well

Make `Process` inherit from Task
Create a OWESRFWidget which inherit from OWWidget and implement stuff for the task graph.