Allow privileged code to get any and all accounts

This is useful for testing. It requires specifying None rather than
defaulting for safety

vanth/platform/ofxaccount.py

@@ -18,7 +18,9 @@ def get(user_id):
         vanth.tables.OFXAccount.c.uuid,
     ]).where(
         vanth.tables.OFXAccount.c.source == vanth.tables.OFXSource.c.uuid
-    ).where(
+    )
+    if user_id:
+        query = query.where(
             vanth.tables.OFXAccount.c.owner == user_id
         )
     results = engine.execute(query)