Add Flask-Migrate to the project

Also moved old migrations to old_migrations folder (before deleting them entirely).

old_migrations/0024_add_options_to_query.py

@@ -0,0 +1,10 @@
+from redash.models import db, Query
+from playhouse.migrate import PostgresqlMigrator, migrate
+
+if __name__ == '__main__':
+    migrator = PostgresqlMigrator(db.database)
+
+    with db.database.transaction():
+        migrate(
+            migrator.add_column('queries', 'options', Query.options),
+        )