Replace storage backend 'pillar' with 'local'

The backend 'pillar' is obsolete; 'local' is the modernity and uses our
nice storage API.

pillar/api/file_storage/__init__.py

@@ -363,7 +363,7 @@ def generate_link(backend, file_path: str, project_id: str=None, is_public=False
 
         return blob.get_url(is_public=is_public)
 
-    if backend == 'pillar':
+    if backend == 'pillar':  # obsolete, replace with local.
         return url_for('file_storage.index', file_name=file_path,
                        _external=True, _scheme=current_app.config['SCHEME'])
     if backend == 'cdnsun':

pillar/api/node_types/storage.py

@@ -16,7 +16,7 @@ node_type_storage = {
         'subdir': {
             'type': 'string',
         },
-        # Which backend is used to store the files (gcs, pillar, bam, cdnsun)
+        # Which backend is used to store the files (gcs, local)
         'backend': {
             'type': 'string',
         },