Fix missing import

wo/cli/plugins/sitedb.py

@@ -1,3 +1,7 @@
+from sqlalchemy import Column, DateTime, String, Integer, Boolean
+from sqlalchemy import ForeignKey, func
+from sqlalchemy.orm import relationship, backref
+from sqlalchemy.ext.declarative import declarative_base
 from wo.core.logging import Log
 from wo.core.database import db_session
 from wo.cli.plugins.models import SiteDB