Integrate ewoks v2

TODO

• use widgets from ewoksorange.bindings instead of having a lower level 'ewoks' connection.
• replace 'Inputs.data_table' from est project by a 'converter' widget. Would simplify the process and could simplify thinks. Do the same for output. Especially those 'Inputs.data_table' where used by the spectroscopy add-on and is only handling one spectrum from what I remember.
• add flake8 on CI

To be discuss about

What might be missing from the API:

• ewoksorange.bindings.EwoksWidget:
  • inputsChanged: function to simplify inheritance when some task imputs change (update the GUI)
  • outputsChanged: function to simplify inheritance when some the task is done change (update the GUI)
  • get a task_outputs to match task_inputs