break down store.py into multiple files in a module

+ fix last updated date bug

app/setup/__init__.py

@@ -1,17 +1,21 @@
 """
 Prepares the server for use.
 """
-from app.db.store import Store
+from app.store.store import FolderStore
 from app.setup.files import create_config_dir
 from app.setup.sqlite import setup_sqlite, run_migrations
 
+from app.store.albums import AlbumStore
+from app.store.tracks import TrackStore
+from app.store.artists import ArtistStore
+
 
 def run_setup():
     create_config_dir()
     setup_sqlite()
     run_migrations()
 
-    Store.load_all_tracks()
-    Store.process_folders()
-    Store.load_albums()
-    Store.load_artists()
+    TrackStore.load_all_tracks()
+    FolderStore.process_folders()
+    AlbumStore.load_albums()
+    ArtistStore.load_artists()