migrate examinations to generic model (and start adding mangament)

atlas/models.py

@@ -29,7 +29,6 @@ import string
 from collections import defaultdict
 from helpers.images import image_as_base64, pretty_print_dicom
 
-from anatomy.models import Modality
 
 from generic.models import (
     CidUser,
@@ -44,6 +43,7 @@ from generic.models import (
     QuestionNote,
     SeriesBase,
     SeriesImageBase,
+    Modality,
 )
 
 # from generic.models import Examination, Site, Condition, Sign