rewrite populate.py to minimize db and hdd reads

+ change process name in manage.py
+ update db query to save show albums as single, as an integer
+ enable periodic scans
+ misc

app/migrations/v1_3_0/__init__.py

@@ -297,7 +297,7 @@ class UpdateAppSettingsTable(Migration):
             clean_album_title integer NOT NULL DEFAULT 1,
             remove_remaster integer NOT NULL DEFAULT 1,
             merge_albums integer NOT NULL DEFAULT 0,
-            show_albums_as_singles NOT NULL DEFAULT 0
+            show_albums_as_singles integer NOT NULL DEFAULT 0
         );
         """