Moved ilastik to its own extensions package

tests/test_workflow.py

 import unittest
 
 from conf.testing import czifile, output_path
-from model_server.model import DummyImageToImageModel
-from model_server.workflow import infer_image_to_image
+from model_server.models import DummyImageToImageModel
+from model_server.workflows import infer_image_to_image
 
 
 class TestGetSessionObject(unittest.TestCase):