Make local tracker use partition key for writing data

[skrawcz]

Context:

This is only an issue if you're using the local tracker as a persister to load from.

Behavior:

If you use the local tracker as a persister, and keep the same app_id, but change the partition key, it'll load from the first instance of app_id if you're loading from prior state.

Task:

1. Push through the partition key wherever it makes sense in the local tracker.
2. Adjust the server to read from the new location / know how to read old and new locations.